It is a logical group of related classes and interfaces and that can be used by any language targeting the .net framework.
A class is the generic definition of what an object is. A Class describes all the attributes of the object, as well as the methods that implement the behavior of the member object. In other words, class is a template of an object.
An object is an instance of a class. It contains real values instead of variables.
Dispose method are used for forcefully garbage collection to relase Unmannaged code
Each function is used to iterate each and every element of an object. It is used to loop DOM elements, arrays and the object properties.