Here are the different usages of this tense:
Make sure you also read:Examples of Typical Time Expressions
(The verbs are
He was flying all day.
Yesterday morning the kids were playing.
He was sitting outside for too long.
He was working at 10 o'clock this morning.
While he was jumping, she was watching him.
Dave was hitting the drums and Joe was blowing the trombone.
He was walking when he stumbled and fell.
While they were sleeping, he got into trouble.
He was always resting.
She was always leaving me with all the paperwork.
He was always sleeping on duty.