The thesaurus is a device for finding specific words or phrases for general ideas. A dictionary will tell you many things about a word - spelling, pronunciation, meaning, and origins. You use a thesaurus when you have an idea but do not know, or cannot remember, the word or phrase that expresses it best when you want a more accurate or effective way of saying what you mean. A thesaurus gives you possibilities, and you choose the one that you think is best within your particular context. The range of possibilities includes not only meanings as we usually think of it, but the special sense and force given by nonformal words and phrases (slang or informal).
Writers, speakers, editors and students will find EnglishThesaurus.net is, more than ever before, the most helpful and effective resource of all.