phranque - 12:10 am on Nov 28, 2006 (gmt 0)

just to expand on jim's reply:

a hardware router/firewall will face "the internet" and handle service requests to your IP address.
it translates some or all of these requests to a virtual IP address. (your computer)

you can easily configure the firewall to reject most requests unless they are in response to an outbound request.

for example you can specifically prevent inbound http service requests which would prevent outside access to your apache server.