If you are using the Notes app only to store simple text, then you are missing out on some of its advanced features. You can store images, videos, audio, links, map locations and many other things in Notes. You can also add checklists and tables. Objects stored in notes can be examined and also exported and shared.
Stickies is an app that has been around on the Mac long before Notes, Reminders and iCloud. You can place little notes on your Desktop to refer to while working. You can even have these notes remain on top of other windows. While it doesn't offer some of the advanced functionality of today's apps, it can still be useful as a Mac-only tool for helping you get work done.
Instead of saving links in bookmarks or the Reading List, you can also save them to a Reminders list and the Notes app. This can be useful during research or when you want to share a link of links with students or co-workers.
If you are new to Mac, you may not yet be using the Notes app. This is a handy built-in app where you can store small pieces of text and create lists. When you use iCloud, your Notes sync across all of your devices, so you can create them and edit them anywhere. You can also share notes with other iCloud users.
If you want to take a temporary photo with your iPhone, and not have to remember to delete it from your Photo Library later one, use the Notes app instead. You can take a photo right from the app, and it will appear in the current note, but not your Photo Library. You can then delete the photo from the Note, or the entire note.
A new feature in macOS Sierra and iOS 10 is the ability to collaborate with more than one person in the Notes app. You can create a note and then add other Apple IDs to share the note with. Each person can add and edit the note in real time, or as an ongoing collaboration.
A new feature in Mac OS X 10.11.4 and iOS 9.3 allows you to lock some or all of your notes in the Notes app. You can assign a single password that works for all locked notes in your iCloud account. You can lock and remove the lock on notes on your Mac, iPad or iPhone. This provides an extra layer of security if you store sensitive information in some of your notes.
The Notes app in El Capitan adds all sorts of new features such as checklists, styles and attachments. You can import photos, documents and other files into a note. You can even add web and map links. A new media browser in Notes allows you to view all of the items attached to all of your notes.