The Dock, located across the bottom (or along one side) of the screen, is a convenient place to keep apps, documents, or folders you want to access frequently. To change how the Dock appears, choose Apple menu > System Settings, then click Desktop & Dock in the sidebar. (You may need to scroll down.)| Apple Support
On your Mac, customize Finder windows and tags, change how filename extensions are shown, and set options for the Trash.| Apple Support
Finder sidebar| Apple Support