It all depends on what you want it to do and how much money and patience you have. Generally speaking it is an MP3 music library, GPS navigation, and movie display. Some guys add a cellular based internet connection or a wifi card. In mine I also had OBD2 software for logging and engine management. Another popular thing is to run gaming system emulators on it and play old console games. Some people also hook up new consoles to it, like an xbox 260 or PS3.