An Obsidian Vault is other words for a group of Markdown notes in a folder (structure) that is made using or for Obsidian.
For example: these notes / articles are in my Obsidian Vault. It is my bundle of documentation.
Obsidian vaults can be synched via Obsidian Sync, but this costs money. You can also just use Github. There should also be a way to export your vault to a website, but I personally use Quartz with Github Pages.