Basically where the Receiver (the one being sucked) sits on the Giver's chest, and places their penis into the mouth, and does most of the work in getting themselves off.
The Giver (the one doing the sucking) lays on their back.
Usually they have their legs up, in a tent type position. (an inverted V shape actually)
This affords more comfort for both parties.
The Receiver (the one being sucked) sits on the upper chest of the Receiver.
In this position, the Receiver (one being sucked) holds onto the head of the Giver (one doing the sucking).
This is done to prevent the Giver from pulling too far back, while the Receiver is stuffing their penis in and out of the mouth.
Also generally a favourite position, for giving Facials, for those who enjoy cum all over their face.