A question about wizards

[Wendy]

My 10 year old had a question for me that I can not answer. What is the
difference between a wizard and a warlock? I always kind of thought
that those two names were interchangable, but in the series it seems to
be a special title. So my question is is it just a title in the series
or is it a descriptor of more powers or what? My daughter will thank
you.

Wendy