A 'Divide and Conquer' algorithm is a type of algorithm that breaks down a problem into smaller parts which can each be solved individually. This is kind of like solving a jigsaw puzzle - if the puzzle is too hard to solve by looking at it all at once, you can break it up into lots of little pieces and solve each one individually. Once all the pieces are solved, you put the whole puzzle back together and see the big picture.
In computer science, a 'Divide and Conquer' algorithm takes something complicated like a big math problem, and splits it into lots of simpler math problems. Then, it solves each of them one by one. Once all the problems have been solved, it puts the answers back together to solve the big math problem.