Port 80 is generally TCP (Web traffic)
Port 443 is called SSL, TCP traffic over a secure tunnel. If you can access a bank website, paypal, etc, this port is open. HTTPS:// in an address bar is using 443 as default.
Port 5101 it probably Outlook Express. You'll need TCP/UDP for access there.
By default 80 and 443 should be open. 5101 will be open if they provide you with an email account.
80 - web browsing
443 - secure web browing
5101 - SMTP (email)