Divide and conquer is an algorithmic approach that breaks down a problem into smaller sub-problems, solves each sub-problem independently, and then combines the solutions to solve the original problem. This document discusses divide and conquer, explaining that a problem is divided into smaller sub-problems, each sub-problem is solved independently, and the solutions are merged to solve the overall problem. The approach keeps dividing sub-problems until reaching atomic units that cannot be further divided, and those atomic sub-problems are solved.