What is a tense? It is a grammatical category that helps locate a situation in time. The tenses can be present, past or future.
In many languages, tenses are not as important as in English (in some languages, they don't even exist!).
In the English language, tenses are especially important because they tell us not only about the time but also about the aspect of the verb.
Consider these two sentences:
There are twelve English tenses. I encourage you to read some more. So don't tense up and click on one of the links below.