If you want to become good at speaking the English language, you need to know different English words that will help you express yourself more. The more words that you know, the more versatile that you can be. There are also some mini-differences with the words that you may use that will convey your thoughts perfectly.
Some people are naturally intelligent and they may be good in coming up with ideas but they are unable to express themselves well because they do not know a lot of English words. Do you want to be someone like this all your life? Some are considered to be idiots because they are unable to find the right words to say.