The Simple Past or Past Indefinite Tense

Affirmative

I wrote.
She wrote.
They/you/we wrote.

Negative

I didn’t write.
She didn’t write.
They/you/we didn’t write.

Interrogative

Did I write?
Did she write?
Did they/you/we write?

The simple past tense is used to talk about a past action or event. The time of the action may or may not be mentioned.

I visited him yesterday.
The letter arrived in the morning.
She spoke eloquently.
He looked charming.

The simple past tense is also used in the sense of used to do to talk about a habitual action in the past.

Edison sold newspapers before he became a famous inventor. (Edison used to sell newspapers before he became a famous inventor.)
In his youth he went for a walk everyday. (In his youth he used to go for a walk everyday.)

The Past Continuous

Affirmative
I was writing.
He was writing.
They/we/you were writing.

Negative
I was not writing.
He was not writing.
They/we/you were not writing.

Interrogative
Was I writing?
Was he writing?
Were they/we/you writing?

The Past Continuous tense is used to talk about an action as going on continuously at some time in the past. The time of the action may or may not be indicated.

The children were playing.
It was raining when we went out.
She was writing.
They were waiting.
The child was crying bitterly.
Why were you shouting so loudly?
Was the boy flying a kite?

The past continuous tense is also used to talk about an action which was in progress when another action commenced.

They were sleeping when the thief broke in.
The lights went out when I was reading.

Note that we use the past continuous tense for the ‘background’ action and the simple past tense for the action that happens in the middle.