Yeah, it's like a temporary address for your computer. Each internet provider has a block of addresses that begin with the same few numbers. The last few change to be specific to each PC that uses their service. They used to be static, in that your internet acct, with whatever provider you had, would assign one to you and every time you dialed in, with your modem to theirs, the same IP was assigned to your computer based on your login info. However, this meant that an specific IP was always being used and as more and more people began using the net, IP addresses would dwindle. So more had to be purchased. Providers went to dynamic IP's. It means that over the year you might have 5 different IP addresses, depending on your usage. If someone doesn't use their internet often, that IP address that would have been static and occupied with that acct, now can be freed up for others to use. Then when that person does finally decide to logon, they'll get a different IP...one that someone else isn't using at the moment. So now providers don't need as many addresses as they used to.
Anyhow...IP's used to be displayed everywhere, but as spammers and hackers have become more prevalent, there are ways to hide this info so it's not floating out there for anyone to grab and use for devious purposes.
An IP uses this format: xxx.xxx.xxx.xxx (ie 163.245.996.112, or 146.54.2.135)