With over four billion hours of video watched by 800 million unique users every month, YouTube has confirmed its position as the top video sharing website in the world. Because of that YouTube has become one of the best and most original online marketing tools available. The ads on this platform are usually in sync with the content of the video requested. A promotional opportunity such as sponsoring a video is also possible on YouTube.

With video ads the customer has to pay only when someone chooses to watch their ad, so they don't waste money advertising to people who aren't interested in their business.
Customers can pay according to the number of clicks for the relevant ad
Customers have to pay after 30 days or after reaching their billing limit.
Customer has to set an average daily budget for each AdWords campaign, and then the system will aim to show their ads as much as possible until their budget is met.
When their budget is reached, their ads will typically stop showing for that day.
It’s possible that customer will be charged less or sometimes slightly more than their average daily budget amount on a given day. To help make sure that their ad can run a little more on days when it's very popular.
Can receive up to 20% more in costs than customer’s daily budget, but other days will be capped at a lower amount to make up for it.
Also customer can pay based on the number of impressions that customer receive on the Google Display Network.