Intransitive verbs are the opposite of transitive verbs. Intransitive verbs don’t need an object in the sentence; they’re quite happy without one. Take this sentence for example:
The weather was beautiful at the beach, so we relaxed there for quite a while.
In this sentence, ‘relaxed’ is an intransitive verb because there is no object that it is doing anything to in the sentence. Intransitive verbs can’t have a direct object that they do something to.
Of course, a lot of verbs can be used in several different ways. ‘Relaxed’ for example can also be used as a transitive verb:
Michelle relaxed Jason by giving him a massage.
In this case, Michelle is actually doing something to Jason - she’s ‘relaxing’ him. So, the object that is being relaxed is Jason and ‘relaxed’ is a transitive verb in this sentence.