TomTom HOME is software you install on your computer (Mac OS or Windows) to manage your TomTom GPS PND. If you want to transfer content to your TomTom GO such as adding or removing maps, custom POI databases, maps, voices, or media files you can do this through the TomTom HOME software. You can also plan your trips in advance from the TomTom HOME application.
The software was released at the same time as the 510/910, however it is compatible with more receivers than just those. The TomTom HOME software will work with the GO 510, 910 as well as the 300, 700, RIDER, ONE, and the TomTom GO.