The name should be simple enough for people to remember but long enough to indicate what it is for. For example office is obviously too general, while on the other hand the full names of some institutes are too long for practical use. Postmaster may suggest changes to proposed alias names. A simple alias is maintained entirely by postmaster. This is fine for an alias that is relatively short and doesn't change much.
Postmaster usually updates the central alias file once a day.
A simple form of mailing list reads its address list from a file. It's better for longer lists and for aliases that need to be changed quickly. Postmaster still creates the alias to start with, but instead of containing addresses, the alias contains the name of the file to read from. Changes to the file are effective immediately, since the email system reads the file each time mail is to be sent. When you want to turn over maintaining the file to someone else, just send mail to postmaster, and postmaster will change the ownership of the file, with no interruption.