In grammar a Verb Tense is a form of a verb used to indicate roughly the time when the action described by the verb takes place. Here we talk about 3 basic tenses: Past, Present and Future. (Some people talk about more than 3, however.)
Compare this with Verb Form which is the form of a verb in a particular tense, e.g. present simple, present continuous, etc.
For more, see Verb Tenses & Forms in English Grammar.