What is an IP address?

At a fundamental level, an IP address is a number representing a device on a network.  Expanding upon that, IP is a suite of protocols that facilitate communication between network devices through a process called routing.  In IPv4, there are both private and public addresses.  Public addresses are routable on the Internet, and potentially accessible from any part of the Internet.  Firewalls will often protect the devices behind public addresses to ensure that only trusted traffic is allowed through.  Private addresses are only routable on local area networks (LANs) and can’t directly reach public addresses without the use of network address translation (NAT).