What does a Trainer do exactly?

Whether offered as a challenge, or a genuine inquiry, this questions can be answered in so many different ways.  Yesterday, while in a cafe, the view inspired one possible explanation...

"Trainer's open windows so people can get a clearer view of the horizon."

(I'm sure there's plenty of follow up questions to this too, such as; "Why is the window so unclear to start with?" or "Whose responsibility is it to clean the window?" And for those who think more logically, 'Why are heck are we talking about windows?")

We have a beautiful five-month-old puppy.  As any new dog owner will vouch, when you have a puppy, you seem to spend a small fortune on trying out new products!  Such as the retractable lead we bought to give her more freedom.  These leads have a switch which releases and break the line.  Why am I telling you this? ​...