This book was written for the purpose of teaching people a language. The reader of this book is not required under any circumstance to know grammatical terms in order to learn this language through this book. However, it is helpful to know grammatical terms so that you can advance more quickly through the book. Some grammatical terms will be foreign to those who are proficient in English grammar, and those terms will be explained as the book progresses. Even if a person who wants to learn Gothic does not know any grammatical terms whatsoever, they should still be able to do so using this book. However, it does help. It also helps if you know another Germanic Language, and also some of the shifting laws that are encountered in this group such as Grimm's Law and (in particular) Verner's Law.
The Gothic Language is itself an old one, and a mysterious one at that. The language has never been entirely reconstructed. We can only theorise about certain parts of the language which are not present in the Codex Argenteus and the few other surviving Gothic texts. Keep this in mind.
When learning a language, it is best to think of it in relation to your own. Do not think of the grammar first. If there is a strange letter, think of it as if you were learning your alphabet for the first time - associate each letter with a sound. If you are learning vocabulary, do not think of the words as Gothic words, but ones that are English used in Gothic. Think of the grammar of the language last, but make sure to pay attention to it. This will make the language much easier to learn for you, because you are not stressed to think that you are learning a completely different language, but merely learning new vocabulary and a new way of saying things.