"Reserved Names" are names used by Alpha to name system objects.  These names should not be used when you name objects.

To find a list of these names, open your A5 control panel.
Click View (on top menu)
Click Code Editor
Give focus to the Xbasic Explorer (Click the wrench icon or "View/Xbasic Explorer")
Click the + for Objects
Click the + for System

You are now looking at a list of named system objects in Alpha Five.  These are present in all A5 databases.  To avoid problems, you should avoid using these system object names as the names for variables as well as forms, browses, reports, or other layouts you build; i.e. don't build a form called 'query' or 'controlpanel' or 'dictionary' or 'label'.

Editor's note:  Thanks to Tom Cone Jr. for this tip.