More or less every area of human activity involves a different range of specialised vocabulary, otherwise known as a linguistic register. Knowing the vocabulary associated with a particular activity isn’t essential, but without it you will probably find yourself using complex, convoluted descriptions, which can be frustrating. Once you learn the relevant words, you can talk about the activity with confidence, and those involved with the activity will be more likely to believe you know what you’re talking about. Of course it helps considerably if you know what the words mean as well.
If your car breaks down, for example, and you have to take it to a garage, knowing the words to describe what you think is wrong and being able to discuss possible solutions will signal to the mechanic that you about cars. As a result, he will be less likely to slip some extra unnecessary work onto your bill. By this I’m not implying that all garage mechanics would stoop to such practices, but these things do sometimes happen, apparently.
While in France, I had forgotten the word for Clutch so resorted to “The machine that works the gear box”.
David Sedaris, in his book “Me Talk Pretty One Day,” tells of being in France and needing an umbrella. When he entered a shop he promptly forgot the word for umbrella in French. (I think it’s “parapluie,” but I don’t speak French, so I don’t know.) At any rate, Sedaris went to the shop keeper and said in halting French: “When it rains, my hair is wet.” The shopkeeper found an umbrella for him, and all went away happy.