Email addresses can be obscure and difficult to remember. Most email programs have some sort of address book that allows you to store the addresses you frequently mail to under a nick name. Rather than having to remember your mother's address as dxdg05a@prodigy.com, for example, you could store her address in the address book and give her a nickname like 'mom'. When you are ready to send your mom a message, you can just type mom in the recipient spot, and the program will replace that with her actual address. Much of the time, you can also use such features to group a number of addresses under one name. If for example, you were a manager and wanted to frequently send messages to all members of your department, you could store all such names with a nickname of 'department.' When you send a message to 'department' everyone in the list gets the message automatically.