Plato gives us perhaps the earliest definition of philosophy when he has Socrates say in The Republic that philosophy is the love of wisdom. Unfortunately, that definition doesn't shed much light on exactly what it is philosophers actually do.
Paul Pardi pitches in to help provide a fuller explanation and thereby does a service for introductory philosophy students everywhere by tackling the question of what philosophy is (and isn't) in a post at
Philosophy News. He begins by explaining why philosophy is not science, psychology, linguistics, nor theology even though philosophers address issues common to those disciplines.
What philosophy is, Pardi writes, is a practical framework that leads to truth and which constitutes the foundation of all other subjects. This by itself might not help much, but in his post he explains in more detail what he means by this.
His explanation should be helpful to students trying to figure out what the heck it is they're supposed to be learning in philosophy class.