Timeline helps you pick up where you left off. Clicking the Task View button in the taskbar or pressing Windows Key + Tab summons the feature, which displays a—you guessed it—time line of your activity in supported apps, stretching back over the past. Even more handily, Microsoft lets you group related apps together into “Activities” in Timeline, so that when you open that week-old budget document, for example, the presentations and websites you referenced at the time can be easily summoned as well. This even syncs across devices, so it could be especially useful if you use multiple PCs.
The fly in the ointment: Only a limited number of apps work with Timeline currently, though Microsoft offers tools for developers to bake in support. That includes Office, Adobe’s Creative Cloud, and native Windows 10 apps like News and Maps, but Microsoft Edge is the only compatible browser. Bummer. You can deactivate Timeline by heading to Settings > Privacy > Activity History.