White teas, for the most part are simply plucked from the bush and air dried. There is a misconception that they are unoxidized, they do oxidize a small amount in whatever time it takes it to go from plucked to dried.
White teas are traditionally from southeast China and consist only of buds (see the Flowery White Pekoe). More recently however, new-style white teas have been developed (Mutan White and Sow Mei White) that include leaves with the buds. This brings down the price but keeps much of the delicate sweetness that white teas are so famous for.