IP Address is basically known as Internet Protocol Address. Each computer or device connected in network or to internet needs IP Address to communicate with each other. The main functions of IP Address is identification of host or network along with its location.
IP consists of four decimal numbers each separated by doted decimal's and ranges from 0 to 255. it's a 32-bit number assigned to your computer, router, modem or a network device in order to communicated on a IP network. This 32-bit number is commonly used today and called as IPv4. There is a new 128-bit version of Internet Protocol called IPv6. It's a new addressing system since the IPv4 has shown a enormous growth today.
Internet Assigned Numbers Authority (IANA) is responsible to manage this globally. Then further down the Regional Internet Registries (RIRs) further designates them to Local Internet Service Providers (ISPs). It's then your local Internet Service Provider connects you to internet providing an IP Address though a Dynamic Host Control Protocol (DHCP) or STATIC lease.
Dynamic Lease IP changes when the predefined lease time is over. It can even change on internet disconnection but the STATIC IP Address never changes unless you or your ISP confirms to do so.
Check your IP address (IPv4) shown below