ipaddressinfo.net determines your IP address.
An Internet Protocol (IP) address is a numerical label that is assigned to devices participating in a computer network utilizing the Internet Protocol for communication between its nodes. The original designers of TCP/IP defined an IP address as a 32-bit number and this system, now named Internet Protocol Version 4 (IPv4), is still in use today.
The Internet is a global system of interconnected computer networks that use the standardized Internet Protocol Suite (TCP/IP) to serve billions of users worldwide. It is a network of networks that consists of millions of private and public, academic, business, and government networks of local to global scope that are linked by copper wires, fiber-optic cables, wireless connections, and other technologies. The Internet Layer enables computers to identify and locate each other via Internet Protocol (IP) addresses, and allows them to connect to one-another via intermediate (transit) networks.
The TCP/IP suite is result of a Defense Advanced Research Projects Agency (DARPA) research project on network connectivity. However, its availability has made it the most commonly installed network software. Many versions provide source-code which reside in the public domain allowing users to adapt it to many new systems. Today, essentially all vendors of network hardware (e.g. bridges, routers) support the TCP/IP suite as it is the standard protocol suite on the Internet and in most companies.