An IP address is a unique numerical identifier assigned to every device that is connected to the internet. It stands for 'Internet Protocol' address and is used to identify and communicate with devices on a network. An IP address consists of a series of four sets of numbers separated by dots, such as 192.168.1.1. Each device that connects to the internet has its own unique IP address, which can be either static (fixed) or dynamic (changing). IP addresses are used by computers to send and receive data and they play a crucial role in enabling devices to communicate with each other on the internet.