The detachable unit consists of a 3.5-inch LCD which gets its navigation information from an SD card, and if you opt for TomTom's optional service package it'll provide real time traffic info as well.
There's also an integrated LCD that provides a look at WiFi access information, battery life, network signal strength, and the number of devices connected, with audible alerts and a web admin interface available as well.
So, effectively, the LCD touch panel has two display modes: one mode is an information pad with browser content, and the other functions as a touch panel for the other apps.