When the subject of the sentence performs the action, the sentence is in
. When the subject of the sentence receives the action, and the person or thing doing the action follows the verb, the sentence is in
.
When the subject of the sentence performs the action, the sentence is in the active voice. In the active voice, the subject is the doer of the action. For example, in the sentence "John eats an apple," John is the subject and he is performing the action of eating.
When the subject of the sentence receives the action, and the person or thing doing the action follows the verb, the sentence is in the passive voice. In the passive voice, the subject is the receiver of the action. For example, in the sentence "The apple is eaten by John," the apple is the subject and it is receiving the action of being eaten. In this case, the person or thing doing the action (John) is mentioned after the verb (is eaten).
To determine whether a sentence is in the active or passive voice, you can look for the subject and the verb. If the subject is performing the action and it comes before the verb, the sentence is in the active voice. If the subject is receiving the action and it comes after the verb (often accompanied by the preposition "by"), the sentence is in the passive voice.