There are four past tenses in English. Use them to talk about things that started and ended in the past or things that started in the past and continue to the present.
The simple past tense, sometimes called the preterit, is used to talk about a completed action in a time before now. The simple past is the basic form of past tense in English. The time of the action can be in the recent past or the distant past and action duration is not important.
You always use the simple past when you say when something happened, so it is associated with certain past time expressions
The past continuous describes actions or events in a time before now, which began in the past and is still going on at the time of speaking. In other words, it expresses an unfinished or incomplete action in the past.
It is used:
The past perfect refers to a time earlier than before now. It is used to make it clear that one event happened before another in the past. It does not matter which event is mentioned first – the tense makes it clear which one happened first.
The past perfect continuous corresponds to the present perfect continuous, but with reference to a time earlier than ‘before now’. As with the present perfect continuous, we are more interested in the process.
This form is also used in reported speech. It is the equivalent of the past continuous and the present perfect continuous in direct speech: