Male-Female (or Female-Male) refers to someone who identifies as both Male and Female, is connected to both manhood and womanhood, or whose identity is so interconnected it cannot be separated.
They may identify partially or entirely as Male and partially or entirely as a Female. They may experience these genders simultaneously or their gender can be fluid or flux. One may also identify as Bigender or Androgyne.
It could be distinguished or used interchangeably with Man-Woman, Boygirl, or Werwifgender. Some people identifies with them interchangeably, some people will make the distinction between female/male with woman/man, some people will use Woman-Man but not Boygirl because they feel they are distinctive, some people just have a preference of terms, and a variety of other reasons for people to distinguish between them or not.