If you were blessed with brilliant, enlightened teachers, your experience with grammar has led you to understand not only how to use it but also why it’s essential. However, because you’re holding this book in your hands, I suspect that may not have been the case. More likely, you were blessed with caring, dedicated teachers who followed a pattern of instruction handed down to them from teachers past. That pattern likely focused on memorizing parts of speech and diagramming sentences. And here you are, years later, trying to recall what indirect objects are and why you should care.
First of all, is this word used as an adverb or adjective? And secondly, is my understanding that it talks about teachers from the past who were teaching the teachers who are now teaching you correct?