A greedy algorithm is a problem-solving approach that makes the best choice at each step, aiming for a local optimum. It works by selecting the most immediate benefit without considering the overall situation. This method is often used in optimization problems, where the goal is to find the best solution among many possible options. Greedy algorithms are efficient and easy to implement, making them popular for various applications, such as Kruskal's algorithm for finding the minimum spanning tree in a graph or Dijkstra's algorithm for finding the shortest path. However, they do not always guarantee the best overall solution.