[clivehawkins]

We use the present progressive to describe actions in the present, actions that have an idea of continuity, actions in 'progress'.
For example, It is raining. If you look out of the window NOW you will see the rain is falling at that precise moment. The action of 'raining' is in progress.
Or Peter is eating his lunch. Peter, at this moment, is at the table and has a half empty plate of food in front of him. The action of eating is in progress.

I hope that helps.