we use the SIMPLE PAST to describe something that started and finished in the past.
we use the PRESENT CONTINUOUS to describe a future plan.we use the PAST CONTINUOUS to describe something that started in the past and continues in the present.
we use the PRESENT SIMPLE to describe something that is a state, habit or general truth.
we use the PRESENT CONTINUOUS to describe a temporary situation that is happening around now.
we use the PAST PERFECT to describe something that happened before another event in the past.
we use the PRESENT PERFECT to describe something temporary that was in progress at a time in the past.
Posted by Sankar 
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