When you get baptized, it means that you are officially joining a group of people who believe in a certain religion or way of thinking. Some people decide later in life that they don't believe in that religion anymore or they want to believe in a different one. When they do this, they might want to get baptized again to show that they are now part of a different group of people who believe in something else. This is called rebaptism. It's like changing teams in a game- you wear a different jersey to show that you are now playing for a different team.