A NEW BLOG SERIES - FOR PUZZLED ANCIENTS

For the benefit of old people everywhere (well, those that can read English) I hereby inaugurate an occasional blog-mode that, for want of anything clever, might be called: “Eh?  What’s that mean, sonny?”  My kick-off term is “trope”.  I see it in sentences like: “Oh, just another Internet trope.”  Apparently a “trope” is bad, somehow – but how, and why?  Please explain.