Oh, @Everest, Everest, Everest. Your question makes me forlorn. Language is fun, diverse, and enjoyable!
Words to a language lover are like paint to an artist. You may say something is blue, but the artist would tell you it’s azure. It is the same with language. Different words carry different nuances. To a wordsmith, it’s incredibly satisfying to land on just the right word to describe a thought or idea.
Also, an extensive vocabulary is a fairly reliable mark of an intelligent person. We have some very intelligent people here; this ain’t no Yahoo Answers, my friend.
If you can’t understand something, might I suggest this amazing book called a dictionary? In addition, it probably wouldn’t hurt for you to read more; I’ve been reading since I was about 3 and this is where I picked up the majority of my vocabulary. You will most likely want to expand your vocabulary if you hope to do well on the SATs (you’ll be up against words like triscadecaphobia, truculent, and I can’t remember what else because that was like 300 years ago).