Pinot Blanc is a mutation of Pinot Gris, itself a mutation of Pinot Noir. On the vine it looks remarkably similar to Chardonnay. It is usually made into dry or sparkling wines but especially in Austria can make some excellent early Trockenbeernauslese. On the nose it can be floral or perfumed with hints of apple and sometimes tropical fruits. The fruit remains on the palate and there is a much longer finish than you might expect from a white wine. Of course the sweeter wines incorporate qualities that you might expect from that style.
I have asked winemakers a few times why they chose "Pinot Blanc" or "Weissburgunder" and whether they were for marketing or cultural reasons. Usually the answer has been "It looked better on the label that way".