There are many types of PS1 emulator, developed by various companies and some have been around for more than a decade now. The only difference would be that instead of using the joysticks and gamepads, you would be using the keyboards and keypads to play the game.
PS1 emulator is typically a software application that uses the PlayStation program on a desktop or laptop which enables you to play the games as you would have played on PlayStation 1. Using a PS1 emulator you can play Sony PlayStation games without actually buying the console or the games.