It's a little complicated, but ultimately she doesn't seem to want to label things though she treats me like a full time boyfriend.
Though I also sort of feel like a secret since she's not telling her friends or family about us.
From my previous situation, I suspected that he was seeing other girls and didn't want to risk one of his friends slipping up and him getting busted.
I've heard that they do it to have the comfort of a relationship without ever really having a relationship.
They can keep their options open and won't look like the bad guy/girl since it wasn't clearly defined.
Well you are right, being with or seeing someone is more exclusive than just dating the person, and yes dating a person is just getting to know them to see if you would want to be exclusive with them.
Some persons do not like to put a label on the relationship too quickly, so they say nothing until the feelings are understood.