Why this one over the many other ones available to you? AngularJS has a different approach. Instead of providing a library, it's goal is to make HTML dynamic like most modern web sites are instead of being the old, boring static HTML we're all used to.
Of course, when you first see AngularJS in action, it can look pretty weird. That can be said of a lot of libraries, frameworks, or technologies until you get used to it. I was the same thing when I first started messing with lambdas in .NET.
Below is a small example for AngularJS mostly showing controllers and some basic data binding.
Below is the full demo in action. Note that JSFiddle automatically puts in the html tag, so I had to wrap the body tag with the ng-app attribute for Angular to work correctly.
Another good tutorial is the one from Thinkster. They combine a lot of the articles and tutorials from all over and give them all to you piece by piece along with their own videos.
This was just a very small introduction to AngularJS. While there are tons of other things you can do, this should be good to get something up and going. Once a little bit is understood, the tutorials and all will make so much more sense and you will be able to learn a bit more than you did before. Hope you enjoy learning AngularJS as much as I have!