What an IP address is
An ip address is an address that is used to identify connections on the internet, so that information can be sent to the right person when being transferred back and forth between computers. Everyone who's connected to the internet has his own unique address.
What just your ip address is, is decided by your internet service provider. When you connect yourself on to the net most ISP's give you one automatically which can either be static or dynamic. The most common is dynamic which means it sometimes change, for example when the internet cable is plugged out or a router is restarted. Then it's not sure you'll have the same ip today as you had last week. Static means that it's always the same and never changes.
There are two different versions of ip addressed. IPv4 & IPv6. IPv4 has been used since the internets dawn of time and has a 34 bit format like for example 192.168.1.1. The reason there's two versions is because IPv4 only is enough for about 4.3 billion addressed, which simply is too little for all the worlds connected devices. So IPv6 had be "invented" which instead has a 128 bit format like 2001:db9:46b7:0:0:8u2e:835:1337, and supports more or less an unlimited amount of addresses.
Even geographical ip (geo ip) is used here which shows information about what country, region, city and zip that's registered for the actual ip address you're visiting with. This is totally free open data that's continuously updated and anyone can access. If you have made an attempts to hide your ip address or blocks cookies it will probably show wrong.