The Finder on your Mac
Use the Finder to organize and locate your files. To open a Finder window, click the Finder icon 
in the Dock at the bottom of the screen.
Sync devices. When you connect a device like an iPhone or iPad, you can see it in the Finder sidebar. From there you can back up, update, and restore your device.
Gallery View. With Gallery View, you can see a large preview of your selected file, so you can visually identify your images, video clips, and other documents. The Preview pane shows information to help you identify the file you want. Use the scrubber bar at the bottom to quickly locate what you’re looking for. To close or open the Preview pane, press Shift-Command-P.
Tip: To show filenames in Gallery View, press Command-J and select “Show filename.”
Quick Actions. At the bottom right of the Preview pane are shortcuts that let you manage and edit files directly in the Finder. You can rotate an image, annotate or crop an image in Markup, combine images and PDFs into a single file, trim audio and video files, or create custom actions through Automator workflows (for example, watermarking a file). To learn more, see Perform quick actions in the Finder on Mac in the macOS User Guide.
To show the Preview pane options in the Finder, choose View > Show Preview. To customize what’s shown, choose View > Show Preview Options, then select the options for your file type.
Tip: Select a file and press the Space bar to open Quick Look. You can sign PDFs; trim audio and video files; and mark up, rotate, and crop images without opening a separate app. To learn more about Quick Look and markup features, see View and edit files with Quick Look on Mac and Mark up files on Mac in the macOS User Guide.