What is the port listening command?

Here is my story; bare with me, it does pertain to UNIX:

I have Intego Netbarrier installed. Last night I was surfing around in Firefox. I don't know if any of you know how Netbarrier work, but it lets you allow or block an outgoing connection from a specific program.

I opened Netbarrier up and looked at my Firefox settings. And it had a list for port 7000 and port 8444. If I remember correctly, port 7000 was blocked and 8444 was allowing outgoing connections through Firefox.

The thing that scared me, was that I don't remember ever being asked to set those rules for Netbarrier. And I'm wondering if something could be trying to use these ports for malicious activity.

I was wondering how do I find out what, if anything is using port 7000 or port 8444? I've used lsof -i but I'm kinda confused on how to read it. I don't see anything listed that lists the ports being used. I'm a Terminal newbie. Any help would be greatly appreciated.

And if you have any enlightenment on my first couple of paragraphs, that would be awesome. Thanks.