membership renewal

1. If someone signs up for a paid membership, say $1.99 a month, and it is set to serial, does the member have to manually renew each month or does it automatically renew them, thus billing them again automatically.

2. I plan to use PayPal for this, so are there any special config I need to do in regard to PayPal for the auto or semi-auto (whichever the answer to my first question) in order for it to work?