AMAB is Assigned Male at Birth meaning typically born with genitalia interpreted as a penis but is sometimes due to parents/doctor choosing if the baby's genitalia is not a penis or vagina.
Likewise, AFAB is Assigned Female at Birth meaning typically born with genitalia interpreted as a vagina but is sometimes due to parents/doctor choosing if the baby's genigalia is not a penis or vagina.
AMAB is Assigned Male at Birth meaning typically born with genitalia interpreted as a penis but is sometimes due to parents/doctor choosing if the baby's genitalia is not a penis or vagina.
Likewise, AFAB is Assigned Female at Birth meaning typically born with genitalia interpreted as a vagina but is sometimes due to parents/doctor choosing if the baby's genigalia is not a penis or vagina.