When something is true, legitimate or right, you can say it's correct, using the word as an adjective. It can also be a verb; to correct wrong answers is to adjust them to make them right.
The origin of correct can be found in the Latin word regere, "to guide," which became correctus as the past participle of corrigere, meaning "to straighten." When you correct your posture, you sit up straight. Sometimes when your cell phone tries to correct your spelling you can end up with some amusing sentences.