We already know that .NET Framework=CLR+BCLs (mainly). Like CLR, BCLs also play a very important role in the .NET app development. BCLs are predefined libraries developed by the Microsoft team that provide a set of functionalities (E.g. Interaction with databases, Interaction with Web etc.) to develop a .NET app. As the number of functionalities is at peak, the classes or interfaces associated with these functionalities are also at peak. So it is difficult for a user to consume them. For this purpose “Namespaces” were defined.

        A Namespace is nothing but a group of classes or interfaces that have similar functionalities. These namespaces are created in a hierarchical format. We can define even our own namespaces.
E.g.1. All classes or interfaces related to Web are grouped under “System.Web” namespace.
E.g.2. All classes or interfaces related to Database are grouped under “System.Data” namespace.
E.g.3. All classes that we create manually like first1, first2 etc. can be kept under a namespace like MyNameSpace (which is user defined namespace).

        This grouping of classes or interfaces under a namespace has following advantages:
-There is a possibility of having classes or interfaces with same name under different namespaces.
E.g. System.Console (predefined console class placed under predefined namespace) and MyNameSpace.Console (user defined console class placed under a user defined namespace).
-This grouping will help the developer to consume the classes in a user friendly manner as he will be able to find them in a hierarchy.

        The following diagram shows some basic functional groups of BCLs and then some namespaces associated with each functional group: