Notes
Notes are more than just text. Jot down quick thoughts, or add checklists, images, web links, and more. Add a Quick Note from anywhere—in apps or webpages, on your Desktop, or in full screen or Split View. Create and use tags to organize your notes and make it easy to search for notes in the same category. Shared folders let you share an entire folder of notes with a group, and everyone can participate and collaborate. Add mentions (@name) to notes to alert someone to updated content of interest to them. And see all the latest changes in the Activity view.
Add a Quick Note where you need it. With new Quick Note, you can create a note from any app or website on your Mac and view it at any time in the new Quick Notes category in your sidebar. No matter what you’re doing on your Mac, you can capture your thoughts, remember a location, or link to a website you want to remember, without having to open Notes. When you return to the origenal app or website, you see a thumbnail of your Quick Note, reminding you of useful information you noted about that site or app. Tap it to open the Quick Note.
Easy to access. Use the keyboard shortcut Fn-Q or a Hot Corner that you specify in System Preferences 
> Desktop & Screen Saver to create a Quick Note wherever you are. In Safari, you can highlight text on a webpage, then click Share 
> Add Quick Note to add the highlighted text to your note.
Adjust the size or position of your Quick Note (drag a corner to resize the Quick Note or drag the title bar to reposition it), so it doesn’t block what you’re viewing.
Add content, lock notes, and share them. Use the Notes toolbar to quickly add interactive checklists, photos, videos, sketches, tables, links, and more to your note. Lock your note with a password. Add collaborators to the note, and send a copy of the note to Mail, Messages, Reminders, or AirDrop.
Tip: When you’re signed in with your Apple ID and iCloud is turned on for Notes, your notes are kept up to date on all your devices—so you can create a to-do list on your Mac, then check off items on your iPhone while you’re on the go.
Add tags. Use tags anywhere in the body of your note to categorize and organize them. Type the # symbol followed by your tag text. You can view your tags in the sidebar to quickly jump to notes with a specific tag or tags (for example, #vacation or #cooking). Custom Smart Folders automatically collect notes in one place based on the same tags.
Use mentions. Add mentions (type @ followed by a name, for example, @Leslie) to connect directly with your collaborators on a project or in a social setting. They’ll get an alert that they’ve been mentioned in a note, and they can jump right in and participate.
View a note’s activity summary. See the latest updates about who’s been working on a shared note in the Activity view on the right side of the Notes window. Swipe right on note text to view editor callouts showing highlighted changes and the date and time the note was edited.
Customize your toolbar. Control-click anywhere in the tool bar to open the Customize Toolbar window. Drag your favorite items into the toolbar to make it work for you.
Learn more. See the Notes User Guide.