What does "wait on" mean?

Also, wait upon. Serve, minister to, especially for personal needs or in a store or restaurant. For example, Guests at the Inn should not expect to be waited on—they can make their own beds and get their own breakfast. [Early 1500s]

Make a formal call on, as in They waited on the ambassador. [c. 1500]

Also, wait upon. Await, remain in readiness for, as in We're waiting on their decision to close the school. This usage, a synonym of wait for, dates from the late 1600s but in the mid-1800s began to be criticized by many authorities. However, by the late 1900s it had come into increasingly wider use and is again largely accepted.