Port function and scanning

Dear Group,

Having recently had troubles with intrusion into my PC I have
contacted this group and received a great response.

May I aks for further help. I would like to get answers to the
following questions:

1. Is there a good internet document describing ports, their
function and role, particularly for the windows OS?

2. Are there trustworthy port scanning services available?
Is for example http://www.auditmypc.com/firewall-test.asp
one of them?

Thank you