Learning English vocabulary is a basic and very important part of learning the language. Learning a new word means more than just understanding what the word means. To really learn new English words, you must understand them and be able to use the words correctly when you speak or write.
English has a large with an estimated 250,000 distinct words and three times that many distinct meanings of words. However, most English teachers will tell you that mastering the 3000 most common words in English will give you 90 to 95% comprehension of English newspapers, books, movies, and conversations.