Here is a cropped excerpt from the Wikipedia entry on visual novels:
A visual novel is an interactive fiction game featuring mostly static graphics, usually with anime-style art. As the name might suggest, they resemble mixed-media novels or tableau vivant stage plays. Visual novels are commonly called dating sims in the West—a misnomer, as visual novels are classified as a sub-genre of adventure games and not simulation games. This has led to confusion with the other genre known as dating sims, which often shares a similar visual format with visual novels, but has gameplay based on statistics.
Visual novels and ADVs are especially prevalent in Japan, where they make up nearly 70% of PC games released. They are rarely produced for video game consoles, but the more popular games are sometimes ported to systems such as the Sega Dreamcast or the Playstation 2. The market for visual novels outside of Japan, however, is small.
Visual novels are distinguished from other game types by their extremely minimal gameplay. Typically the majority of player interaction is limited to clicking to keep the text, graphics and sound moving (most recent games offer 'play' or 'fast-forward' toggles that make even this unnecessary). Most visual novels have multiple storylines and many endings; the gameplay mechanic in these cases typically consists of intermittent multiple-choice decision points, where the player selects a direction in which to take the game. This style of gameplay has been compared to the Choose Your Own Adventure books. Some shorter works do not contain any decision points at all. Most examples of this sort are fan-created. Fan-created novel games are reasonably popular; there are a number of free game engines and construction kits aimed at making them easy to construct, most notably NScripter, KiriKiri and Ren'Py.
Many visual novels use voice actors to provide voices for the characters in the game. Often, the protagonist is left unvoiced, even when the rest of the characters are fully voiced. In the typical visual novel, the graphics comprise a set of generic backgrounds (normally just one for each location in the game), with character sprites superimposed on these; the perspective is usually first-person, with the protagonist remaining unseen. At certain key moments in the plot, special event CG graphics are displayed instead; these are more detailed images, drawn specially for that scene rather than being composed from predefined elements, which often use more cinematic camera angles and include the protagonist. These event CGs can usually be viewed at any time once they have been "unlocked" by finding them in-game; this provides a motivation to replay the game and try making different decisions, as it is normally impossible to view all special events on a single play-through.
Many visual novels are centered around romantic themes, but games centered around science fiction, fantasy fiction, and horror fiction are not uncommon.
Visual novels and ADVs are especially prevalent in Japan, where they make up nearly 70% of PC games released. They are rarely produced for video game consoles, but the more popular games are sometimes ported to systems such as the Sega Dreamcast or the Playstation 2. The market for visual novels outside of Japan, however, is small.
Visual novels are distinguished from other game types by their extremely minimal gameplay. Typically the majority of player interaction is limited to clicking to keep the text, graphics and sound moving (most recent games offer 'play' or 'fast-forward' toggles that make even this unnecessary). Most visual novels have multiple storylines and many endings; the gameplay mechanic in these cases typically consists of intermittent multiple-choice decision points, where the player selects a direction in which to take the game. This style of gameplay has been compared to the Choose Your Own Adventure books. Some shorter works do not contain any decision points at all. Most examples of this sort are fan-created. Fan-created novel games are reasonably popular; there are a number of free game engines and construction kits aimed at making them easy to construct, most notably NScripter, KiriKiri and Ren'Py.
Many visual novels use voice actors to provide voices for the characters in the game. Often, the protagonist is left unvoiced, even when the rest of the characters are fully voiced. In the typical visual novel, the graphics comprise a set of generic backgrounds (normally just one for each location in the game), with character sprites superimposed on these; the perspective is usually first-person, with the protagonist remaining unseen. At certain key moments in the plot, special event CG graphics are displayed instead; these are more detailed images, drawn specially for that scene rather than being composed from predefined elements, which often use more cinematic camera angles and include the protagonist. These event CGs can usually be viewed at any time once they have been "unlocked" by finding them in-game; this provides a motivation to replay the game and try making different decisions, as it is normally impossible to view all special events on a single play-through.
Many visual novels are centered around romantic themes, but games centered around science fiction, fantasy fiction, and horror fiction are not uncommon.
Firefly's goal is to translate freeware (doujin) visual novels. There are sites dedicated to translating original stories, but our goal is to translate boys love games based off of pre-existing series (similar to scanlating, say, a Final Fantasy doujinshi instead of an original-character doujinshi). Some of our releases will contain sexual content.
Do I Have to Pay?
No. Some doujin games are commercial, but as they are much more difficult to obtain outside Japan, we feel that making patches for buyable games would only encourage piracy. We will translate demos of commercial games, but we will not make a patch for any commercial game unless there are specific circumstances. All our releases will be provided for free.
What's Your Policy on Translating These?
We take a slightly different approach here. Before localizing any game, we will send an email to the game's original creator requesting permission to translate it. If the creator refuses permission, or does not reply, we will not go ahead with the translation. There will be no exceptions to this. We'd like to keep this respectful to the creators; this is a smaller, more personal community.
Explain your usage and age policy
Some of our works detail two men in sexual acts and are made for adults. Please learn your age of consent policy in your country and abide by it. Though some of our other works are light (noted with a rating on their project pages), we strongly request you do not download these works until you are considered an adult in your country of origin. If downloading such items is illegal in your country, we are not held accountable by your actions.
Will you translate [title of game]?
As explained in our translation policy above, we can't make any promises, but if you know of a game that fits what we do and we don't have it listed as a possibility, let us know!
Please keep in mind that we do not have the resources to decrypt certain game engines' filetypes, so it's possible we won't be able to do it.
What Operating System are these Games For?
Depending on the game engine, the games will either be Windows-only or for both Windows and Mac OSX.
I Can't Get [Title of Game] to Work!
Unless it is a specific issue with the game script itself, please do not contact us with any problems running games. If you are running Windows, try setting your locale to Japanese in the Regional and Language Options.
Can I post graphics/art from these games on my LiveJournal (or community) or use them for wallpaper/layouts/icons/etc.?
Certain artists request that their graphics and artwork not be redistributed; we would like to honor their wishes, so as a general rule, we do not allow graphics or art to be reused.
How can I contact you?
We prefer being contacted through e-mail at firefly.vns[at]gmail.com. However, please read all our FAQ before contacting us, and DO NOT contact us about your personal issues in downloading or running our releases. Please also note that reply times may be slow.
So when can I expect the next release?
This site's releases will be fairly sporadic, so don't be surprised if we go for several months without a release. Visual novels take much more time and effort to localize than a scanlation.