Think of the Base as the lowest priced trim, designed to attract environmentally conscious drivers on a budget. This trim doesn't have cruise control, heated mirrors, or the other minor perks you get in the Liftback and Touring trims. Otherwise, its basic standard features match those of its sportier siblings.
Think of the Liftback as 2007's Base trim and one step up from 2008's Base trim. It doesn't look quite as sporty as the Touring trim and therefore serves as the midlevel Prius.
The Touring serves as the premium choice among the 2008 Prius's triumvirate of trims. It includes 16-inch wheels, a refined suspension, and some nice exterior features, including extra-bright headlights and a rear spoiler.