Mission Control in macOS Sierra allows you to create multiple desktops with different windows on each. You can easily create these desktops and move between them with keyboard shortcuts. This allows you to go between apps and workspaces easily, saving you time and effort. You can also use full-screen apps as a desktop. This is handy for MacBook users in particular as screen space is limited.
If you use Mission Control, you can assign an app to a specific desktop so when you launch it it automatically appears on that desktop instead of the current desktop. You can also assign an app to appear on all desktops, which is handy for note-taking and other tasks.
Split View is an underused viewing mode where you have exactly two apps on your Mac's screen at once. It is similar to Full Screen mode and works in conjunction with Mission Control.
Get to know the new Lion gestures. You can use a trackpad on a recent MacBook or a Magic Trackpad to navigate around in Mac OS X 10.7 Lion. You can also do some gestures with a Magic Mouse. See where to enable and customize gestures.