WHILE, (JUST) AS, WHEN:
They show that two actions happen in the same time
-ex. He was doing his homework when she was listening to music.
THE MOMENT, AS, SOON AS, WHEN, ONCE:
They show that one action happens immediately after another
-ex. The child fell asleep once he climbed into the sofa.
BY THE TIME, BEFORE, AFTER, UNTIL/TILL:
They show that one action has happened before another
-ex. The train had left by the time we arrived.
It shows the beginning of an action or a situation
-ex. We have been working simce this morning.