Theory exam ...er, what it says on the tin ... an exam/test to determine that you know the theory - air law, rules, how the blasted thing works!!!
I think the other confusion is "hire". As a private pilot you are not available for hire as that would be commercial work for which you are not qualified.
However, you will be able to hire an aircraft for your own pleasure and to take friends and family flying. You will not be able to earn any money from this.
Cheers
Whirls