That's a big question you need to be more specific. If you want the truth, then English has only 2 tenses: present and past. What the books uusually call tenses are a combination of these and aspects (e.g. continuous or perfect) and/or future markers such as "will". A good understanding of aspects will help a lot in your studies. However, a full explanation with examples is too long for here and, depending on your current level, may be difficult to understand. If you just want a traditional explan ation and a table with the "tenses" laid out in it any good student's book will provide you with that - alternatively try "How English Works" by Swan and Walter ISBN 978-0-19-431456-5.