K before I start, these are actually two questions but are technically related!
1- I'm still not sure what the difference is between a controller and template_controller. Can't you use the same functions in both of them?
I suppose you can compare a template_controller with some kind of master page? But even so, you can apply the same code to both of them, no?
2-Let's say you include content using the following codes:
view
The Template Controller is just a normal controller with a few conventions included. We say that Fuel is as conventionless as possible, so we make this template functionality as an optional extra you can use if you have read the documentation and understand it.
It essentially has a master "template" view which acts as a wrapper. So instead of $this->response->body you do $this->template->body and the response will be wrapped in your "wrapper template".