What is Vo2 Max or maximal oxygen consumption, maximal oxygen uptake, aerobic capacity?

Vo2Max determines the cardiovacular fitness of an individual. it is the volume of oxygen used by the muscles for contraction in a unit of time.
The muscles need energy for contraction, with the help of oxygen and few other elements energy(ATP) is created. This energy feuls muscle contraction. Thus the better the supply of oxygen the longer will the activity last.
Oxygen reaches the body via the Lungs, the lungs pass it on to the blood and the heart pumps it all around the body.
Oxygen is supplied to the muscle by blood vessels, the muscles extract the oxygen from the blood vessels and use it to create energy needed for muscular movement.

This phenomenon of providing and extracting oxygen to the muscle is the Vo2max = V - volume per time, O2 - oxygen, max - maximum.

It is essential for any athlete to have a high Vo2Max, whatever the sport. The Vo2Max is a indirect indicator of the individuals overall health. It is a standard for measuring physical fitness.
In endurance sports the greater the Vo2Max the longer and faster the sportsperson will perform.
In strength sports if the individual has a high Vo2Max then the formation of harmful chemicals or metabolites(lactic acid) is minimal and the sportsperson can maintain a set for longer duration for max strength gains.