Transitive verbs have an object. They can be contrasted with intransitive verbs, which do not need an object.
'I like chocolate', 'What are you looking for?' and 'She's always wanted a little girl' are examples of transitive verbs.
In the classroom
One area to be careful of when teaching transitive and intransitive is verbs that can be both. For example:
'We leave on Friday' is intransitive 'Don't forget to leave your keys' is transitive. Some teachers avoid labelling verbs as transitive or intransitive, preferring to focus on meaning. This then indicates whether the verb takes an object or not.