everyone plays chrono on a "rom". wtf is that?! i grew up playing on psone and snes...the rom is a program for the computer or something? where can i get it and how much does it cost?!
Cartridges use "ROM" chips to store data. It's just another way to represent bits by hardwiring their values into a chip. Unlike disk drives though, ROM chips can be accessed like regular memory using the address bus, which is why cartridges don't have loading times.
What most people on the Internet call "ROMs" are just copies of the data made from ROM chips on cartridges and stored in files (usually with some added information in a header that specifies things like the size of the chip and the system type). Technically, you'd call them ROM images, where image in this case means a complete copy of all of the data stored in one medium copied into another medium.
Since part of the data from ROM images for things like SNES games includes the actual code segments (programs) for the games, you can write PC programs that analyze parts of the code and pretend to do what real SNES hardware would do with it (take input, draw to the screen, access data in the ROM). That's all an emulator is, just a program to interpret the machine code for another type of computer.
Since most published games are copyrighted (and will be for another half century or so), it's illegal to download ROM images of games. Most games have a software license on the back or in the manual that also prohibits you from making copies of games you already own.
Technically, the copyright owner of the game could sell ROM images or license others to sell them, but nobody's bothered making a business model out of it, since illegally available ROM images of games are all over the Internet.
In other words, never pay for a ROM image, because it's almost always being illegally copied and sold.
Also, we don't want to advocate copyright infringement here, especially the sort that can hurt Square-Enix's business, so don't use the forums to pass around links to sites that provide illegal copies of copyrighted material like games.