Questions about Unity Ads implementation

Hi, i am trying to implement UnityAds but it got me really confused. Every tutorial shows something else.

What is the difference between UnityEngine.Advertisements and the Monetization Asset from the Assetstore ? Do i need both ? When i use Advertisements, why can’t i choose the Banners position as written in the Documentation? If i need to implement both, why not make on holistic asset for the Adsystem ?

Thanks for your help !

Another opinion, hop that can help: [Guideline] How to transform your 2D Game idea to Final Product in ONE MONTH. - YouTube

Here is some official documentation on implementing ads: