Slip, Slip Socket, Socket, S and SOC
All refer to a "female" end that will accept a male fitting into it.
Street, St, Spigot, SPG, SP
All refer to a "male" end. It glues into another fittings socket.
MPT and MIPT
Both refer to a "male" fitting that is threaded to fit into a female pipe thread (see FPT below)
FPT and FIPT
Both refer to a "female" fitting that is threaded to accept a male pipe thread (see MPT above)