Its obvious: if ads play and you click or buy, the advertiser makes money... same thing for any other ad.
To host videos and to make money through ads.
you don't put the ads on , they just appear whilst being viewed
If people watch the videos, they must click on the AdSense ads posted in order for you to get paid.
Yes, YouTube video previews are safe. Adsense and Google are aware of this and don’t penalize sites for using them. If the preview links to a site that isn’t safe, the search engine will definitely penalize the site for that.
In order to make money on YouTube, you need to make videos that people enjoy watching. If people like your videos and subscribe to them, then you can partner with YouTube and share in the revenue that YouTube makes off of ads that they run on your videos.
If you mean the ones in the videos, I don't think you can. Those are being put in there by the owner of the video.
Once you get to a certain amount of subscribers you can register for a youtube "partnership", or maybe somebody like adsense will send you a message to put their ads on your videos and will pay you for each time somebody clicks on it.
Yes it does.
A professional YouTuber is a youtuber who has several hundred (more likely thousand) subscribers. The youtuber has ads on the side of their videos and sometimes and the beginning of them (the youtuber does not put the ads in them self. it is automatically added). Because of the ads on the videos, the youtuber gets paid. it takes great work to become a youtube partner (or as said before 'professional youtuber'). many videos, much work in advertising your channel, money into making videos look nice (i.e. buying a nice camera. nobody likes to watch fuzzy videos). editing genius also comes into play. jokes. appeal. It takes lots of hard work to be a 'professional' at anything. Even youtube.
You do not get directly paid for posting a video on YouTube. There are however ways to receive money for posting videos on YouTube. If your videos become extremely popular, you will receive some money for allowing YouTube to show ads while your videos play. There are also third party apps such as ClipSponsor which allow you to receive donations from anyone for videos that you post on YouTube (in case they find your videos useful or inspiring or funny).
It depends on how many views you get. since you are getting the money from the ads placed on or before your videos, the amount of views your video gets greatly contributes to the amount of people who are going to see those ads therefore contributing to the amount you get paid.
YouTube shows ads because they need and want to make money, like every other content provider. They are also hoping more ads will annoy people into upgrading to the YouTube premium service which is ad-free.