A packet is a block of information. ANYTHING you send or receive over a network is broken down into packets. (Imagine the London Bridge. They broke it down brick by brick, labeled them, shipped them to AZ, and reassembled. That's what happens when you send or receive anything over a network)
the number after the colon is the port number. I'm not sure if that's the incoming port or the source port. Probably the incoming, meaning, the packets were trying to address those ports.
A port is a virtual address that networked computers use. For instance, port 80 is for websites. When you request a website from a server, your request is routed to port 80, so that whatever program is acting as a web server, gets the request.
You probably don't need to worry about it. Zone Alarm is blocking them, so whoever is sending them is wasting their time.