Break up the opponent's moyo
Two white frameworks stand on this board, and they ask different questions. The bottom-left one is small and solid — built from a corner enclosure, hard to live inside; against such thickness you reduce, playing lightly near its rim so the stones are never trapped. The top-right one is looser — a wide lattice with room in its belly; that is an invasion target, where a deep stone can find life or at least destroy enough ground to pay for itself. Choosing correctly between invade and reduce is worth more than any single move inside either framework: first classify the framework, then pick the tool. Black to play: classify, then act.
White has built frameworks. Black to play — invade or reduce.
Play one of the marked points to finish this lesson.