Past tense: I went to work yesterday. (main verb: go)

Past tense negative: I didn't go to work on Sunday. (main verb: go)

Past continuous tense: I was eating my breakfast when the phone rang. (main verb: eat)

Past continuous tense negative: I wasn't eating anything when the phone rang. (main verb: eat)

The past continuous tense is often used to show one or more two past actions.

What was the boy doing at the park?

He was making sand castles.

The boy was making sand castles while playing in the sand.

This boy made sand castles while he was playing in the sand.

I was drinking coffee while I was working on my computer.

sounds better than...

I drank my coffee when I worked on my computer

....because there's some activity.

You were taking English classes when you visited the United States.

or

You took English classes when you visited the United States.

(Both verb tenses are okay)

He was talking on his cell phone while he was walking to work.

or

While he was walking to work, he was talking on his cell phone.

(Many sentences that use "while" are continuous)

Past tense:

He talked on the phone an hour ago.

She was talking on the phone while she was drinking coffee.

or

She was talking on the phone while drinking coffee.

(Notice "she" is missing from the second sentence. That's okay.)

It was snowing when this man went out to shovel his driveway.

("It" refers to the weather.)

We were standing in my classroom when this picture was taken.

("was taken" is passive voice--not continuous. Notice the difference?)