Prosperity Gospel basically is the kind of gospel that is being preached all over the world that tells you that whatever you ask... you receive. Taking away your sight towards the cross and makes you focus on God's magical talent. No longer will you be called to repent of the sins you have committed but being invited to gain the life that you want, instead of losing it for His sake.
In this video, John Piper offers a little perspective on what he thinks about this kind of gospel. Check it out.