Screen Time is a feature that Apple added to iOS 12, which allows you to keep track of how much time you spend on each app you use, how many times you wake up your iOS device, and how many notifications you receive. This data can help you cut down on your device usage, and you can use Screen Time to set limits for your kids.
Screen Time was also added to macOS Catalina, with the same features. However, it doesn’t seem to work correctly. Rather than showing which apps are frontmost when you work, it shows how long apps are open.
I chalked this up to beta weirdness over the summer, but it seems that Screen Time on the Mac is just … bad.