Internet Protocol version 4. Wherein unique addresses are assigned to devices (viz, computers) in a series of four numbers (called octets) seperated by decimals, like so:
That particular number corresponds to google.com. There are reserved addresses that are not routable -- notably 127.0.0.1, 172.16.0.0/16, 192.168.0.0/16, and 10.0.0.0/8. These addresses are reserved for local networks and will never be routable beyond them.