Firstly, it represents nothing - it enables us to write in symbols the fact that nothing is left, or there to start with.

Secondly it enables us to make an empty space in a number. For example in the number 650,081 the zeros tell us there are no hundreds and no thousands. Without the zeros our place value system would not work as we would not be able to distinguish 650,081 from 6,581.

But we also use zero to mean other things. Often we use it to create a reference point. For example:

When we talk about the height of land we mean its height above sea level. This means that someone decided that sea level would be at zero height.

The freezing point of water is zero when measuring temperature in centigrade but not in Fahrenheit. The freezing point of water is 32 degrees Fahrenheit. Zero Fahrenheit was the coldest temperature that the German-born scientist Gabriel Daniel Fahrenheit (after whom the scale is named) could reach with a mixture of ice and salt.

"Absolute zero" is -273.15 degrees centigrade. Absolute zero relates to the oscillation of molecules or atoms. In all materials a point is eventually reached at which all oscillations are the slowest they can be. This point is called 'Absolute zero'. You can never reach absolute zero.