Markdown

Markdown is a file format and syntax for writing documents in plain text [1].

The benefits of using Markdown over something like Microsoft Word/docx or OneNote is its simplicity and portability [2].

NOTE

Since the files are just plain text, if you're tech-savvy, you can use code to search or manipulate documents programmatically.

References

1. https://en.wikipedia.org/wiki/Markdown
2. https://obsidian.md/