As projects become larger and the number of scripts increases, the likelihood of having clashes between script class names grows ever greater. This is especially true when several programmers are working on different aspects of the game separately and will eventually combine their efforts in one project. For example, one programmer may be writing the code to control the main player character while another writes the equivalent code for the enemy. Both programmers may choose to call their main script class Controller, but this will cause a clash when their projects are combined.
To some extent, this problem can be avoided by adopting a naming convention or by renaming classes whenever a clash is discovered (eg, the classes above could be given names like PlayerController and EnemyController). However, this is troublesome when there are several classes with clashing names or when variables are declared using those names - each mention of the old class name must be replaced for the code to compile.
The C# language offers a feature called namespaces that solves this problem in a robust way. A namespace is simply a collection of classes that are referred to using a chosen prefix on the class name. In the example below, the classes Controller1 and Controller2 are members of a namespace called Enemy: