Last night at 6 PM, I was eating dinner.
At midnight, we were still driving through the desert.
Yesterday at this time, I was sitting at my desk at work.
while + long action (past continuous tense): I was sleeping
When the telephone rang, I was sleeping.
While I was sleeping, the telephone rang.
There are 4 basic combinations:
While Ellen was reading, Tim was watching television.
Were you listening while he was talking?
I wasn't paying attention while I was writing the letter, so I made several mistakes.
What were you doing while you were waiting?
Thomas wasn't working, and I wasn't working either.