while
used in time clauses
If one thing happens while another thing is happening, the two things happen at the same time.
He stayed with me while he was looking for a new house.
While I was out she was trying to reach me on the phone.
‘while’ in concessive clauses
While has a special use which is not related to time. You use it to introduce a clause that contrasts with something else that you are saying.
Miguel loved sports while Julio preferred to read a book.
While I have some sympathy for these people, I think they went too far.
‘a while’
A while is a period of time.
After a while, my eyes got used to the darkness.
Let's just sit down for a while.