The mapobject database is for all the mapobjects (POI, Shops, etc)
Per default it is initialized as a sqlite3 database in mapserver.sqlite
If you want to store your mapobjects in a proper database or need performance at
scale you can configure a postgresql server in your world.mt:
pgsql_mapserver_connection = host=127.0.0.1 port=5432 user=postgres password=enter dbname=postgres
The syntax is the same as for pgsql_connection