Intransitive

A verb is called intransitive when no action transfers from their subject to an object, e.g.

She sang beautifully (No object in this sentence - beautifully is an adverbial)
He swam like a fish (No object in this sentence - like a fish is an adverbial)
They died (No object or adverbial in this sentence)

A transitive verb takes an object - the thing that takes its action,
e.g. He [S] hit [V] his thumb [O] with the hammer [A].