1 Corinthians 13:4 (NKJV)
Envy is defined as an awareness of an advantage of some kind that someone else has, and the desire to possess it. This "advantage" could be some material thing, or it could be a position that another person has, or some favor that was shown towards someone else. Often, envy and jealousy are seen as the same thing, although not everyone might agree with that. The point is that when someone has, or is doing, something that you are not, and you wish you had what they had, that is envy.
In Galatians 5:21, we are told that envy is a work of the flesh, 1 Corinthians 13:4 tells us that love does not envy, and Romans 5:5 says that the love of God is in our hearts. From these verses we can see that if we have envy over something that someone else has, it is something coming from the flesh, from our natural desires, and not from the love of God that is in us. If we are envious about something, it shows us that we are being motivated by the wrong desires and looking to the natural rather than the spiritual side of life.
If we are envious, then we are focusing on the wrong thing, and instead of trusting in God and what He can do for us, we are comparing ourselves to others and giving in to the idea that somehow someone has some advantage over us. God loves us and if we put our faith in Him then He will supply whatever we may need, just as much as He has done for anyone else, so there is no reason for us to envy or covet what someone else has. We need to walk in love and be glad for the good things we see in the lives of others.