The defining element and the very essence of the Maldives are the coral atolls. Aesthetically and aquatically stunning geological formations that captivate from the first moments where the long haul jet is coming into the area on arrival. One of the first questions visitors have is ‘what are these things and how did they get here.’
Wikipedia has good article on Atolls and their formation including animation of atoll formation shown above. Britannica also has a similar illustration, but annotated with terms here.