IP Address you may have heard that term thrown about, by your technician, friend, commercial, etc....
Well there are Entire Books dedicated to the TCP/IP Protocol - so I am going to give a quicker run down.
Every device connected to a standard network has to have its own IP Address. For example 192.168.0.x
Also to communicate without a router the devices have to be in the same range such as the first three octets in the above example would be the same on every device, and only the last octet would change from 1-254.
The reason they have to be unique is for example if your neighbor three streets over had your exact address, the post office wouldn't know where to send the package, same goes for network packets.
Most of the time your IP Address is assigned by a DHCP Server, which keeps track of who has what, and how long they are valid. You can tell when the DHCP Server can't be reached by the little ! on the network connection by the clock says Limited or no Connectivity. Not to mention your Internet Stops Working:)
Talk to you next time, Thanks!