Past Continuous Tense is used:

To describe an unfinished action that was interrupted by another event or action.

To express a change of mind.

To describe the background in a story written in the past tense.

With the verb 'wonder' to make a very polite request.

A boy was eating vegetables when his mom called him.

The girl was going to the theatre but then decided to go to the library.

Children were playing until their moms came.

The dog was running to the park but turned and ran to the house.

He was sleeping deeply, until his alarm clock rang.

He was watching TV, until his favourite programme finished.

She was cleaning the window, until the dirt vanished.