Knowing the proper lingo helps you communicate. The same piece of lumber could serve as a stud or a rafter. The difference lies in how you use it. It's equally important to know where to place the support beams. It could fall down around you.
Language works the same way.
Nouns, verbs, adjectives, adverbs, pronouns, conjunctions, and prepositions are the building blocks of English. You can write without knowing your parts of speech, but you run the risk of faulty construction. If you know the basics, your writing will be much stronger. Once you have a handle on the parts of speech, you will begin to understand how words work. Almost any word can be more than one part of speech depending on its purpose in a particular context.