What happens in the build phase?

What happens in the build phase? Who calls this phase?
Does the phase build of the parent call the build phase of the child, or the phase build is done by the type_is::create() (what exactly happens in the create()?

In reply to saritr:

You may want to see Calling of build phase? | Verification Academy

The create() method is just one way of constructing a class object using the factory - it has nothing to do with phases. What matters to the build_phase() is that all its child components are constructed when the parent build_phase returns.

In reply to dave_59:

But what happens in the type_id::create() ?

In reply to saritr:

See what is the use and advantage of create() method instead of new() method while creating a handle of a class? | Verification Academy