Second, they organize your application.
Namespaces tell the compiler what software needs to be present in your programming environment and in the finished system so you can package it and send it out to customers. They provide the naming link that ties the library files in your system to your program code. Namespaces are the 'container' for classes, structures, enumerations, delegates, and interfaces - stuff that you'll learn more about as you get deeper and deeper into VB.NET.
In fact, your application is automatically created as a namespace in VB.NET. If you create a new windows application, VB.NET names the project WindowsApplication1 by default. Open Solution Explorer and click the project name. Click on the Project menu item and choose Properties to display the project dialog. You will see that the Root Namespace is WindowsApplication1.