What is Activity Monitor and how do I use it?

Activity Monitor shows you every app running on your Mac and how much CPU, memory, and energy each one is using. Open it from Applications → Utilities → Activity Monitor whenever your Mac feels slow. Look at the Memory tab to find which app is using the most RAM — that's the culprit.

Activity Monitor is a built-in tool that shows you what programs are running on your Mac and how hard they're working. It tracks memory, CPU, disk space, network speed, and battery drain. If your Mac is slow or a program is frozen, Activity Monitor tells you which app is the problem so you can close it or restart it.