A blowjob where the Receiver (the one being sucked) is generally seated on a chair or sofa, while the Giver (the one sucking) is on their knees, performing oral sex.
The Receiver (one being sucked) generally is leaning back, into a chair or sofa.
The Giver (one doing the cock sucking) is usually on their knees in front.
While not a romantic position, it is one that does the job efficiently, allowing full access to the Giver, to the genitals (of the Receiver).
In a semi reclining position, it affords easy access to the scrotum, and allows for some digit exploring, if desired.
Allows greater comfort to the Receiver, so they can enjoy seeing the action, or close their eyes and imagine it all.
Many don't care to have their head controlled, however this position does allow for that.
It also allows for the Receiver to help keep any of the Giver's hair from falling into their mouth, while they are performing their deep throat technique.