OpenWebAuth used to be called “Magic Auth”, because of how seamless the experience is. Instead of only being able to manage things from your social dashboard, you can jump from one part of the Fediverse to another, and your permissions will be granted automatically. It all happens in the browser.
The way this works is relatively simple: your browser accesses a token inside of a cookie. That token references your Digital Identity in the Fediverse, verifies it, and a handshake is performed. Afterwards, anything you were given permission to access unlocks and becomes visible on the page.