Obsidian is a what-you-see-is-what-you-get personal wiki and markdown editor. It is by no means unique; there are many similar markdown editors such as org-mode in Emacs, Notion, OneNote of Vscode. What distinguishes it from other tools is that it is aesthetically pleasing and has an active user base and surrounding the idea of knowledge bases.
I use Obsidian because a lot of other people use it and it has an active community of plugins. I used to use emacs org-mode to do similar things. I use a tool like Obsidian, a personal knowledge management system as something “hold my hand” while working and development.
This cookbook is dedicated to how get things done in Obsidian, often using Plugin Repl a tool that I wrote.