Capture a quick thought or save something important or interesting for later. It’s quick and easy to create a new note in the Notes app. And you can access upgraded iCloud notes on all your devices with OS X v10.11 and later or iOS 9 and later, and on iCloud.com.
To create a new note, click the New Note button 
in the toolbar (or use the Touch Bar) and start typing. You can also quickly create checklists that you can complete over time. Learn more.
Drag and drop pictures, movies, links, and other files into your notes. You can also add content to notes while using Safari, Photos, Maps, or many other apps. Learn more.
You can have your notes with you no matter which device you’re using. For example, you can save a recipe on your Mac, then have easy access to it on your iPhone when you’re shopping for ingredients. Learn more.
Do you have notes with private information? You can lock them to keep your content secure. Learn more.
Or, if you want to collaborate with others, you can add people to your notes and allow them to contribute and add their own updates. Learn more.
Siri on your Mac makes it even easier to use Notes. You can create a quick note, have your notes read to you, search for a specific note, and more. Here are some examples of what you can say to Siri:
“Create a new note”
“Show me my notes”
“Show me notes from last week”