Original: A proximity fuze (also called a VT fuze) is a fuze that is designed to detonate an explosive device automatically when the distance to target becomes smaller than a predetermined value or when the target passes through a given plane.
Simplified: A proximity fuze (also called a VT fuze, for "variable time") is a fuze that is made to create an explosive when the distance to the target becomes smaller than a set value or when the target passes through a given line.