Obsidian is a free note-taking app but differs from text documents or sticky-notes in that notes are saved as Markdown files, which allows for a feature-rich experience. If you've ever wanted to build your own wiki or knowledge base, this is the way to go. Files are stored on your personal device, but there is paid option that allows for cloud syncing across devices. You can also just host them on GitHub or any other cloud storage for free, but there will be extra steps if you want to sync to other devices.

It comes with features like database and graph view, infinite canvases, etc. There's also a host of plugins to customize it however you want.

This site is published through Obsidian notes using the 01 Home plugin.

Notes

Help Page
https://help.obsidian.md/

Basic Markdown syntax
https://help.obsidian.md/syntax

Callouts
https://help.obsidian.md/callouts

Advanced

Tables, diagrams
https://help.obsidian.md/advanced-syntax

Mermaid
https://mermaid.js.org/#/