Lets clear one thing up so everybody understands:
Press-up is usually used by the English and push-up is generally used by Americans, however they still mean the same thing.
This is a great strength building exercise great for building the endurance of the muscles shown in (1).
It is a very common exercise even practiced by infants who copy their parents actions.
The drawing image of the muscles below (1) used in this strength training exercise shows which muscles are used which include many of the same muscles as are used to do a pull-up.
Muscles such as the pectorals, trapezius, deltoids and the serratus anterior among others are used during this exercise.
There are many variations of the press-up, the image (2) below being one of them.
I will be posting more variations of this exercise soon.
The press-up being demonstrated in stages is called a Hindu press-up for example.
The motion of this press-up is as much up and down as it is round and round, picture the motion of a piston within a car engine.
When performing a press-up try to keep your posture as good and straight as possible so it can support itself and deter from strain.