Complex sentence: An Off-Off-Broadway production that features members of Actors Equity is, of necessity, called an Equity Showcase production; not all Equity Showcases are considered to be Off-Off-Broadway.
Split into simpler sentences: An Off-Off-Broadway production that features members of Actors Equity is, of necessity, called an Equity Showcase production. Although not all Equity Showcases are considered to be Off-Off-Broadway.