What is the difference between an IP address and a MAC address?

They identify a device at different levels and for different purposes. A MAC address is a permanent hardware address burned into the network card by the manufacturer; it is 48 bits, written in hex like 00:1A:2B:3C:4D:5E, and it identifies the physical device on a local network. An IP address is a logical address assigned by the network or an administrator; it can change when you move to a different network, and it identifies where the device is so data can be routed across the internet. A good analogy: the MAC address is like your fixed name, while the IP address is like your current postal address, which changes if you move house. Data travels using IP addresses between networks and MAC addresses within the local network.