"Catalyst::View::Component::SubInclude" allows you to include content in
your templates (or, more generally, somewhere in your view's "render"
processing) which comes from another action in your application. It's
implemented as a Moose::Role, so using Moose in your view is required.
Simply put, it's a way to include the output of a Catalyst sub-request
somewhere in your page.
It's built in an extensible way so that you're free to use sub-requests,
Varnish ESI () or any
other sub-include plugin you might want to implement.