Can a verb be both transitive and intransitive?

Answer 1

Actually, yes, a verb can be transitive and intransitive depending on the sentence. The verb eat, for example, is transitive in this sentence: "I ate an apple," but is intransitive in this one: "Lindsay already ate."
Other verbs can be both as well, such as "play," "clean," and "read."

Verbs are transitive when they precede a direct object, and they are intransitive when they do not.

Answer 2

Because it can show what the verb is doing.

Transitive' is the opposite of 'intransitive'.

A transitive verb takes an object, e.g. 'I eat the apple'

An intransitive verb does not have an object, e.g. 'I worry'
.
(On the other hand, if you change the meaning of this particular verb, it can become transitive, as in: 'The dog worries the bone', where there IS an object, viz, 'the bone')