port 1080 & firewall setup

psr

Can somebody explain in very simple terms, the following statement in Interwoven Knowledge Base Article: 49145.

Using Vdiff's "Source Difference" through Firewalls.

Clicking on "Source Diff " opens up a connection to TeamSite server on port 1080.
This is from Client machine to port 1080 on TS, right?.
If the TeamSite server is being accessed through the firewall then the port 1080 needs to be open and should allow,
outbound TCP connections through the firewall to the TeamSite server.
How requests & response here differes from other requests?