It's an expensive high end GameBoy clone, basically. It uses some specialized hardware (FPGA) to run original GB cartridges and can also run other retro consoles pretty well. It's a bit nicer than most other handheld emulator devices that are on the market right now, although it's limited in some other ways.

A Game Boy clone console that can play original Game Boy (Color/Advance) cartridges with a terrific screen and support for many more systems' ROMs via OpenFPGA.