The impl keyword works in a very similar way to a function. The structure of an implementation needs to considered as being closer to a static class (in C#) or as a function within a function:

impl MyImpl
{
  fn reference_name (&self) ... 
}

This would be more for a non-generic type. For generics, the preceding code becomes the following:

impl <T> MyGenericImpl<T>
{
  fn reference_name(&self) ... 
}

Note that the <T> is required to tell the compiler that the impl is for a generic. reference_name is the name used to access the impl function. It can be anything you wish.

If you build and run the impl_example code, you will get a result like this:

The code creates two implementations for two functions that provide a defined functionality.

The impl_example is a very simple example. An impl can be as complex as required.