Topic: How tile maps work - Beginners
Was reading up on Web Mercator (The map "layout" that Online Maps, Google, Bing and many others use) and found a top notch document by microsoft on how everything with tile maps work. If your new to tile maps this is definitely worth a read!
Note that this information is not needed to use Online Maps (I mean this asset works out of the box) but certainly recommended to understand how the system works behind the scenes.
Online maps uses both Web Mercator projection and Quadkeys, both explained quite well in this article.