When we were talking about action verbs, we defined the two different kinds like this:
A TRANSITIVE verb is an action verb that has a direct object.
while
An INTRANSITIVE verb does not have a direct object.
That's not too painful, but if you don't know what a "DIRECT OBJECT" is, the definitions above aren't going to help you much. This video does a nice job of explaining:
This video does a great job of explaining Indirect Objects: