Passive voice

What is the difference between the active and passive voice?

We usually try to write in the active voice because it’s easier to understand. 

In the active voice the subject ‘does’ the action: 

Notice how the subject in these examples is 'doing' the verb's action. 

The boy is the subject and he is doing the eating.

But in the passive voice the action is performed 'on' the subject. So we can say the subject is 'acted on.' 

The cake is the subject and it is acted upon.