team member = new account?

I am using the trial version of the web app.  I was allowed to invite another user to be a "team member" but I cannot find anything about "team members" in the manual.

I wish to know:  If I open an paid account, and wish to have 2 other people be able to view, download, edit, etc., must I pay for 3 users (@$99/year each) or can they just be "team members".?