Intercourse refers to any penetrative sex between two partners of any gender or sexual orientation. In the most traditional sense, intercourse refers to heterosexual sex, the kind that involves inserting a penis into a vagina. But there are other types of penetrative sex; anal sex, oral sex, fingering or the use of a strap-on dildo could also be considered intercourse in some contexts.
Intercourse may also be called copulation or coitus.