What does "inner" mean?

Inner: Not obvious or easily discovered; obscure. Inner house (Scot.), the first and second divisions of the court of Session at Edinburgh; also,the place of their sittings. -- Inner jib (Naut.), a fore-and-aft sail set on a stay running from the fore-topmast head to the jib boom. -- Inner plate (Arch.), the wall plate which lies nearest to the center of the roof,in a double-plated roof. -- Inner post (Naut.), a piece brought on at the fore side of the main post, to support the transoms. -- Inner square (Carp.), the angle formed by the inner edges of a carpenter's square.