Obsidian is the latest in a long line of note management software I have tried over the years. My goals have been notes in a text format for ultimate portability. Initially that was raw txt files. Eventually that changed into Markdown md files, to support some basic formatting while still remaining portable text files.
Obsidian uses a “vault” to hold all of your Markdown notes. This vault is nothing more than the top-level folder for your note structure. Obsidian adds a few config and index files, but otherwise your collection of notes is a folder structure however you want it to be.
Obsidian also has extensive plugin and theming support, so you can make it be whatever tool you need, and look however you want it to look.
There is also a paid service called Obsidian Sync that can synchronize your notes across platforms. Personally I use iCloud for my underlying sync’ing solution.
There is also Obsidian Publish which can push your digital garden on the web hosted by Obsidian. I run my own web server, so I need more control so Obsidian Publish isn’t a great fit for my needs.