Joplin is an Open Source note-taking application that can handle a large number of notes organized into notebooks.
Notes are stored in markdown format and can be searched, modified, tagged directly in Joplin or using any text editor. Evernote users can even import their notes.
Joplin has no learning curve. It's so well laid out that you can jump right in. Across the top, you can quickly create a new note, to-do, or new notebook. You can toggle the sidebar on or off and even change the layout.
Like any good text editor, there are numerous font options, including bold, italic, copy, paste, and more.
Best of all, while you can download the portable version and take it anywhere, you can also sync to your favorite cloud service, including Dropbox and OneDrive.
As mentioned, Joplin is an excellent, well-thought-out program. The layout is simple to use right away, so there's no learning curve. There are many things that you will find intuitive and work as expected. If you take a lot of notes and need to organize and back them up, you'd be hard-pressed to find a better note-taking program, and that's saying something.
The author accepts donations, which can be done by going to the author link above or Help, Donation inside the program.