A sentence can be said either in the active voice or the passive voice. In the active sentence, the subject is the “doer” of the action. For instance, consider the following two sentences:

“John opens the door.” (active)

“The door is opened by John.” (passive)

In the first sentence, John is the doer, and the situation is depicted from the doer’s standpoint. However, in the second sentence, the situation is depicted from the standpoint of the object (i.e., the door) instead. In this passive sentence, the focus is not on the doer but on the object of the action.