Aerobic respiration is the release of energy from the glucose or another organic substrate in the presence of oxygen. Strictly speaking aerobic means air, but it is the oxygen which is necessary for aerobic respiration.

Here is glucose molecule. A glucose = carbon + hydrogen +oxygen

This is a much more accurate formula :

Glucose + Oxygen = Carbon Dioxide + Water + Energy

You should be able to see six carbon atoms on each side of the equation; One molecule of glucose contains six atoms of Carbon and six molecules of Carbon Dioxide each contain one atom of Carbon.

You should also be able to see that the Hydrogen is balanced. One molecule of Glucose contains twelve atoms of Hydrogen and six molecules of water each contain two atoms of Oxygen.

Now look at the Oxygen. To make six molecules of Carbon Dioxide we need twelve atoms of Oxygen and to make six molecules of water we need another six atoms of Oxygen. That makes a total of eighteen atoms of Oxygen. The glucose already contains six atoms of Oxygen so the cell will need a further six molecules of Oxygen from the air.

Aerobic respiration takes place in almost all living things. It is easy to get rid of the Carbon Dioxide and excess water; this is excretion (the removal of the toxic waste products of metabolism), and maximum energy is released from the glucose.

Here's a interesting video glucose song to help you memorize better