Within Activity Monitor, you’ll see a barrage of constantly changing numbers and app names, but don’t panic. These screens are actually pretty simple to navigate. The first tab, CPU, shows how much processing power each running program requires. (CPU stands for Central Processing Unit; this component acts as the brains of the computer and performs most of its calculations.) You’ll see all open programs in the column on the left, along with the percentage of processor time they’re currently taking up. The bottom of this tab will show you the overall CPU usage with a constantly updating graph.