Tense

The Simple Present and the Present Continuous

Veabs are said to be in the simple present form if the action denoted happens often or is repeated
The action can be a daily routine or a hobby or a scheduled event
 - Do you drink coffee
 - My mother leaves home at 9 o'clock every day.

Verb are in the present continuous form if the action denoted is happening at moment of speaking.
It is raining
I cannot come with you. I am doing my homework now.

The Simple Past and the Past Continuous Tenses

The simple past tense is used to describe an action that happened in the past
 - John met Richard yesterday.
The past continuous tense is used for actions that continued for a while before the new action interrupted them.
- He was sleeping when the phone rang.
Blue = Past progressive
Green  = Simple Past

The first part of the sentence describes something that continued to happen before a new action

Will and Going to

Will is used with the base form of the verb to talk about that may happen in the future

 - I will complete the essay tomorrow

 - George is very talented. He will become famous one day.

Going to is used when we talk about a decision or a plan made before the moment of speaking

 - I am going to invite all my friends