An open exhibition is an exhibition that anyone can submit work for inclusion in (geographical limits are sometimes set). Entries are selected based on merit and appropriateness. The exhibition is usually high profile and often prestigious.
Typically a charge is made for entry; this money helps to fund the exhibition, as does a percentage commission charged on any sales.
Many Art Societies use Open Exhibitions as a way of attracting and/or selecting new members. Public or community-based organisations like museums and municipal art galleries also hold Open Exhibitions, as do some commercial galleries.