You can Monetize a channel meaning YouTube place ads on your videos and share the revenue with you. Not sure of the exact figures but I know YouTube take about 40% of the revenue. Also all content must be your own creation otherwise copyright holders can claim the content. 3 copyright strikes and your channel is shut down. If you planned to post say football footage recorded at a game I think you'd be in murky water regarding content ownership.
If the viewer bypasses the advert nobody gets revenue. You used to be able to avoid adverts by using a console (xbox or ps3) and still can on some mobiles. AdBlock also means the view won't trigger the advert.