Adding description to your interface helps you to identify the interface. If all your ports have interface description, using commands like #show interface description,or #show interface status will give you the status, type, and description of each port. This will save you lot of time when trouble strikes and device goes offline if you implement it as part of your network documentation. It also helps the other Administrators identify interfaces at your absent.
Configuring an interface description:
Switch1(config-if)#description Lan connection to Legal Department 3rd floor