Traditionally a heterosexual sex position, this is one that Lesbians, with a strap on dildo, can better perform, than any man on man scenario.
Girls just wanna have fun too, and this is a great sex position for two females.
Then too, most heterosexual positions can be well enjoyed by two females, while some, are not available for man on man sex.
This really isn't a natural type of position, nor an easy one, when it comes to the actual entry (penetration)
Basically, the Receiver (the one being penetrated) lies down flat, and unlike most sex positions, they keep their legs closer together. (now you know why penetration can be difficult, downright impossible for two guys.)
The Giver (the one doing the penetrating) sits astride of the Receiver, facing in the same direction.
They place their legs astride of the Receiver.
Their knees are closer to the chest of the Giver, and the legs are folded underneath, the feet in the direction of the feet of the Giver. They are not flat on the surface, that is for the lower legs.
Insertion (penetration) can be difficult, and should be done with caution (due to strap on dildos not allowing for any feeling to the wearer), however the tightness does afford greater pleasure to the Receiver.
During insertion, using a dildo, one should be cautious, to avoid possible damage or injury, during the act of penetration.
Pegging is the term used, for when a strap on dildo is used in place of an actual penis.
Of course, a simple dildo or other object, can be used, but a strap on affords the Giver to have their hands free, for other fun stuff.