What is the difference between postgraduate degree and postsecondary degree?
A postgraduate degree is a degree you get after your
undergraduate degree, so for example a Master's degree or a Ph.D. A
postsecondary degree is a degree you get after high school (high
school = secondary school), such as a B.A. or B.Sc.
A postsecondary degree is usually referred to as an
undergraduate degree. (At least in my neck of the woods.)