Jealousy or envy is a feeling (or emotion) people get when they want what others have. This is a negative feeling. When someone is jealous of someone else, they usually dislike the other person. These particular emotions are usually caused by a person having a certain object or quality which you desire but can not obtain. Jealousy is caused by lacking of self confidence and judging your abilities.
Under rational observation jealousy is not reasonable. Feeling jealous of something that someone else has isn't helping you get what you want, instead of feeling jealous, one should simply try and obtain the things that one wants instead of acting in a jealous manner. For example: Being jealous of someone's car. Instead of being rude about said car or bad mouthing person driving said car, work hard to earn money to acquire a similar car, then the jealous feelings should disappear.