English parts of speech :

The Future :

The future simple is used :
 - for predictions : what you think will happen or what is certain to happen.

e.g. You are going on a long flight.

The future continuous is used to refer to a future continuous action.

e.g.  You are going on a long flight.

Past Perfect Tense :

The present perfect is used to refer to actions which take place in an
unfinished time period up to the time of speaking.

The present perfect continuous tense is used to refer to an action
    which started in the past and continues today.
e.g. I have been learning English since September.

The present perfect simple is used to refer to the finished part of
    a continuous action.

e.g. I have learnt new vocabulary.

The present and past continuous :

The past simple tense is used to talk about finished actions in a finished period of time, 

for example :

Yesterday evening I played tennis with a friend.

Present Simple Tense is used:

1. To talk about regular activities ( e.g. John plays tennis once a week )

2. To talk about tastes (e.g. Peter likes Chinese food )

3. To talk about facts (e.g. The sun rises in the east )

Do we need to study grammar to learn a language? The short answer is "no". Very many people in the world speak their own, native language without having studied its grammar. Children start to speak before they even know the word "grammar". But if you are serious about learning a foreign language, the long answer is "yes, grammar can help you to learn a language more quickly and more efficiently." It's important to think of grammar as something that can help you, like a friend. When you understand the grammar (or system) of a language, you can understand many things yourself, without having to ask a teacher or look in a book.

Grammar is the system of a language. People sometimes describe grammar as the "rules" of a language; but in fact no language has rules*. If we use the word "rules", we suggest that somebody created the rules first and then spoke the language, like a new game. But languages did not start like that. Languages started by people making sounds which evolved into words, phrases and sentences. No commonly-spoken language is fixed. All languages change over time. What we call "grammar" is simply a reflection of a language at a particular time.