"NEBULA is an emulator for CAPCOM CPS2 recreational arcage game machines (Street Fighter, Marvel and Dungeons&Dragons characters)"
There are many classic arcade games that could pass into history because no one has a copy or even the console they were played on. Fortunately there are clever people who invent software which emulates them, like this NEBULA. As you can probably work out by now, NEBULA is an emulator for CAPCOM CPS2 hardware. Among the arcade games available for this hardware are Street Fighter (2, Alpha etc), and games with characters from Marvel and Dungeons&Dragons.
NEBULA is one of the best emulators on the market as it allows you to have multiple players, who can play connected via the Internet, and it supports all kinds of cheats. If you are good at programming you can also add games that are not included but are supported in the game list, simply by using DAT files. This emulator also works using the MAME naming system, so any mame-compatible game that is supported should have the same name.
To play any of these games in NEBULA you need the motherboard ROMS and some decryption tables. You can find them all on the author`s website.