Activity selection is a problem in optimization where the goal is to choose the maximum number of non-overlapping activities from a set, each defined by a start and finish time. The challenge lies in ensuring that selected activities do not conflict with one another, allowing for efficient use of time and resources. This problem can be solved using a greedy algorithm, which involves sorting activities by their finish times and then iteratively selecting the next activity that starts after the last selected one. This method is effective and widely used in scheduling tasks in various fields, including computer science and operations research.