Push ups

The push up is an exercise designed to strenghten the core and chest and arm muscles

Movements

Shoulder:
extension/Flexion
Scapula:
Retraction/protraction
Elbow
Flexion/extension

Muscles

The push up is one of the oldest upper-body strength-training exercises available. It is great because you can do it pretty much anywhere.
Problem is that most people are still struggling to do this exercise right. So the key here is to watch the video and practice. Not everyday but about 3 times a week each with a rest day in between

How to do it

The pushup starts with you lying on the floor in a prone position with your feet together.
Your hands should be flat on the floor pointed forward and under your shoulders, and you should be on your toes with your feet pointed down.
From this position, you will push your body off the ground until your arms are straight, making sure the back and legs stay straight
Slowly return to the start position.

Exercise Tips:

Squeeze your butt
Align arms with shoulders
All the way up, all the way down
Active shoulderblade movement (your shoulders blades should come together on the way down and separate on the way up)