CHIP-8 is a simple programming language used on microcomputers and game consoles in the 70s. It sees no practical application nowadays and is only an educational exercise to practice low-level programing. Many game ROMs are freely available on the internet .
If you can't stop yourself from trying it out: download a ROM, upload it where it says "Select executable...", then hit "Play". Depending on the game or program it might take a few seconds to get running. Mind you, the technology is old and this emulator hardly efficient.
The original CHIP-8 keyboard is mapped to a modern QWERTZ / QWERTY keyboard using the mapping in the above image to the right.