What does it mean exactly when you have a friend with benefits?

I am in somewhat of a situation, this woman and I have been texting for about 2 weeks now. I’ve never had a friend with benefits.

So….To what extent does it go?
I mean how much of friend am I suppose to be? How important is sex?

Guess if we ever find another person or something, no big deal right?

Since it is pretty straight forward with that part anyways she made it clear she wanted to be friends first, then friends with benefits later. I’m not exactly against this, but sometimes I feel like she had might as well be my girlfriend…...

Any advice here?