Leather subculture is about BDSM, or that part of it that associates closer to S&M and fetish or to Homosexual BDSM.
Leather fetishism describes an attraction to people wearing leather, or to items made from leather.
Old Guard leather (also Old Guard but not to be confused with fascist movements of that same name) is the gay leather subculture from which much of BDSM originally derived.
New Guard leather (also New Guard or just New Guard) is a more sexually-liberated and less protocol-driven version of the Leather subculture.
Leather Family describes a family or family-sized-group living in an alternate lifestyle often based on the leather subculture or on BDSM.
Leather Community is used to loosely associate people living in the leather subculture or even into the wider BDSM. Roughly equivalent to "BDSMLifestyle"