Intransitive verbs are not used with an object; they relate only to the subject.
She walked the dog.
There’s an object here: the dog. In this sentence, walked is transitive.
She walked in the park.
In this sentence, walked only refers to the subject, so it’s intransitive.
Here are some more sentences using intransitive verbs:
The plane lands at 4:00.
When do you have to leave?
I enjoy skiing.
The puppy looked cute when he sneezed.
N.B. A lot of English verbs can be transitive or intransitive, depending on the meaning. To clearly identify an intransitive verb, make sure there’s no object in the clause.