[AccessD] Alias Table Name

Dear List:
 
In a legacy app I came across some queries which in the QBE had 'alias'ed
tables (or maybe queries).  one called P was joined to one called A.  The
list of field names didn't correspond to any table.  There are a lot of
queries so I didn't look through them to see if a query matched the field
list in either P or A.
 
But I've never seen this done.  Why would you do this?  How can you tell
what the source of the fields in the aliased table is?  Is there some
performance gain or other reason for doing this?

MTIA,
 
Rocky