TENSES

Talking about the present
English has two main ways of talking about present time: the simple present and the present progressive.
THE SIMPLE PRESENT
You make the simple present by using the verb in its basic form. You add ‑s or ‑es to the verb in the third person singular.
The simple present is used in the following ways:
1. You use the simple present to talk about something which is happening now, and which will continue to happen in the future. You often use the simple present in this meaning to talk about things that are true about your life, for example where you live, your job, or the kinds of things you like.
Martin lives in Canada.
I work in a hospital.
"What kind of books do you read?”  “I mostly read science fiction."
2. You use the simple present when you talk about something which happens again and again, or when you say that something happens regularly at a particular time. Use words such as always, often, sometimes, occasionally, and never, or phrases such as on Tuesdays or every day with the simple present in this meaning.
They often go out to restaurants.
I travel to London twice a month.
He gets up at 6 o'clock.
She goes to church every Sunday.
3.  You use the simple present to talk about something which stays the same for ever - such as a scientific fact.
Oil floats on water.
Two and two make four.
4.  You use the simple present when you are describing what is happening at the exact moment when you are speaking. This meaning of the simple present is used for example in sports commentaries.
/.k,Shearer gets the ball from Gascoigne. He shoots ‑ and scores!   For descriptions of actions that are happening now, you usually use the present progressive rather than the present simple. For example:
“What are you doing?" "I’m  making a poster." NOT "What do you do?" “I make a poster.”
THE PRESENT PROGRESSIVE  
You make the present progressive by using a form of the verb be in the present tense,
followed by the main verb with an ‑ing ending, for example l am waiting, she is coming.
The present progressive is used in the following ways:
1.  You use the present progressive to talk about something which is happening now at the time you are speaking or writing. You often use this meaning with words and phrases that express present time, such as now, at the moment, and currently.
“What's Bob doing?" "He's watching television."
It's raining again.
I’m looking for my glasses.
2. You use the present progressive to say that something is happening now, but will only continue for a limited period of time. Compare these pairs of sentences:
We live in France. (="France" is our permanent home)
We're living in France. (="we" are living there for a limited period of time)
He cooks his own meals. (="he" always does it)
He's cooking his own meals. (="he" does not usually do it)
If you want to talk about the subjects you are studying at school or university, you usually use the present progressive.
She's studying law at Harvard. NOT She studies law at Harvard.
I’m studying English. NOT  I study English.
VERBS THAT CANNOT BE USED IN THE PROGRESSIVE
Verbs which express a situation or process, rather than describing a definite action, are not usually used in the progressive. Do not use the progressive with the following verbs:
be                                have                           see
believe                       like                             agree
know                           love                         disagree
recognize                  hate                            mean
remember                  prefer                         need
understand               want                           deserve
wish                            belong
I know the answer.  NOT  I am knowing the answer.
She understands me.  NOT She is understanding me.