This page will give you a quick introduction as to how the Internet - or networking in general - works, at least so far as PeerBlock is concerned.  We'll gloss over some of the details here, but this should give you enough info to at least understand the basics of what's happening.

IP Addresses

An IP address is like the street address of an apartment building, where that apartment building is your computer.  It specifically identifies your computer.  All computers have an IP address, as this is how your computer can "find" other computers - things like website names are just "human friendly" names, the computer really couldn't care less what it's called.  When you tell your web browser to go to www.peerblock.com, it actually check to see what IP address the computer called "www.peerblock.com" is using (174.133.179.10), and then starts communicating with that IP address.

Kind of like a phone number, IP addresses go from general to specific numbers.  For example, in the US phone numbers are in the format 123-456-7890 - the 123 is the "area code", which generally covers many towns; the 456 generally means one specific town; and the 7890 is one specific phone within that town.  (Again, we're oversimplifying things here to make it easier to understand - don't get hung up on the details, just go with it for now.)  Similarly, for an IP address of 12.34.56.78, the 12 could mean "Company XYZ", the 34 could mean "California Branch", the 56 could mean "Building B", and the 78 could mean "Bob's Computer".  Again, it's actually a bit more complicated than that, but this is the general idea.

Ports

If an IP address is like the street address of your apartment building computer, a "port" is like a particular apartment within that building.  Your computer has 65535 ports in it, and every connection your computer makes with another computer goes out of one (generally random) port on your computer, and into a (specific) port on a different computer.

Some ports are "well known" ports - for example that apartment number that's known for having wild parties every Friday night.  Port 80 is generally used for "web traffic", also known as "HTTP"; port 443 is generally used for "secure web traffic", also known as "HTTPS". 

Ports are generally specified as following a colon, after an IP address.  So "12.34.56.78:1234" would mean "IP address 12.34.56.78, port 1234".