A HTPC is usually to be included in the home entertainment system. It becomes part of the living room. What makes it different is the size of the case, it's primary use for media, and even a remote control. Many HTPC have a TV tuner inside it and thus becomes a DVR. It makes use of a TV and there is usually a wireless desktop set. A HTPC acts like a TV, is usually cooler and quieter than a conventional PC, and has more storage space for music and movies.