Fellatio

Fellatio is oral sex performed on a penis. Possible positions include:

Sitting
The receiver lies on his back while the partner kneels between his legs. The receiver lies on his back while the partner lies off to the side of their legs. The receiver sits in a chair the partner kneels in front of them between their legs.

Standing
The receiver stands while the partner either kneels in front of them or sits (in a chair or on the edge of a bed, etc.) and bends forward. The receiver stands while the partner, also standing, bends forward at the waist. The receiver stands or crouches at the edge of the bed, facing the bed. The active partner lies on the bed with their head hanging over the edge of the bed backward. The receiver inserts their penis into the partner's mouth, usually to achieve deep throat penetration.

Lying
While the active partner lies on their back, the receiver assumes the missionary position but adjusted forward. The active partner (with breasts) lies on their back, and the receiver inserts their penis between the breasts, and into the mouth.