The Stable release is the standard full-feature Factorio release.
You may download the headless version intended for use on servers.
To download the full version of Factorio, you can purchase a key or log in if you already have an account.
This is a free publicly accessible demo. It contains only a subset of what is available in the full game.
The purpose of the demo is to teach the very basic game mechanics and let the player decide whether they are interested in more.