Using the active voice makes your writing simple, clear, concise and immediate, drawing your reader into the action of the piece and giving your writing energy. Using passive voice, on the other hand, can make your writing seem too formal, dull and wordy and can create a distance between the reader and the words.

Passive 

In passive sentences, the thing acted upon is the subject of the sentence, and the thing doing the action is usually included at the end of the sentence, for example:

The book was read by Sam.

The book is the subject receiving the action, ‘was read’ is the passive verb and Sam is doing the action.

Active

In active sentences, the thing or person doing the action is the subject of the sentence, and the thing or person receiving the action is the object. So:

Sam read the book.

Sam is the subject doing the…