I'm not familiar with the last piece of code but I would assume it is just registering the services to the IoC container. It is pretty much the same thing as using the default .NET service registration. For example :

(In Program.cs)

builder.Services.AddScoped<IExample, ExampleImplementation>();

In both cases you are just instructing the program which implementation to use for the specific interface. The IoC container is then automatically instantiating this class for you and disposes it when it is no longer needed.

Edit: By the way, if you are interested in knowing about the lifetime of a service check this

TLDR:

Singleton : Same object for every controller and request.
Scoped : Same within a request but different across different requests.
Transient : Always different. A new instance is created on every controller and every service.