Yes, as long as you have high speed internet and a decent WIFI signal you can hook up to your lap top. My wife used it that way for a buiseness phone. As far as phone numbers you can use any number you choose. Magic Jack also makes a cheap pocket sized phone that works just with it. Wal Mart has them for around $10. You have to make sure what ever phone you use is compatible with the Magic Jack or it won't ring. Go to their sight and they have a 30 day free trial. If you like it you pay the $39.95, if not send it back and pay nothing. The first year's service is free.
No a Fax machine won't work with it. It's only for phone service.