As a new language, to understand it, we try to use the concepts of other popular languages to compare with him.
Programs written in Q# end with .qs.
A simplest Q# program also contains the namespace namespace.
C# also has namespace, and a similar concept used in java is package.
There are definitions that reference other namespaces in Q#, you need to use open:
namespace Example { open Microsoft.Quantum.Primitive; // ... }
Java uses import. C# seems to be using.
Within the namespace, developers can define any operations, methods, custom types, etc.
We will learn these concepts gradually.