What are vector Photoshop brushes for?
There is no such option in Photoshop. If you mean Vector
Photoshop shapes then the shapes can be used for infinite things in
Photoshop such as layers, masks, as frames, as a source for
selections, as a source for actual brushes, for patterns, for
exporting to other applications, used in shape blurs, used as
cookie cutters in Photoshop elements.
Illustrator vector brushes exist as do expression and Xara
vector brushes and many others but sadly, as yet, Photoshop has no
vector format brushes.