The line of succession indicates who will sit on the throne in Britain when the reigning monarch dies.
The Queen is now in her 90s and when she dies, Charles will become King.
He is referred to as the heir to the throne, so Charles's son William is the second in line, and William's son George is the third in line. Charlotte, William's daughter, is fourth in line thanks to a change in the law made before she was born, and her younger brother Louis is fifth.
Despite being young, they are all above their uncle Harry in line to the throne, and he stays in line even though he stepped back from royal duties.