What a redirect chain actually is
Type a URL and you rarely land where you typed. Behind the scenes the server often answers not with a page but with a redirect — “not here, go there” — and your browser quietly follows. String a few of those together and you have a redirect chain: http becomes https, the bare domain becomes www, an old path becomes a new one, and only then does the real page load. Most of the time it's invisible and harmless. Sometimes it's two hops longer than it should be, or it points somewhere you didn't intend, and you'd never know from the browser alone.
That's what the tool above is for. As a redirect chain checker it sends one live request and follows every hop, laying them out in order with the exact status code and timing for each. You get to see the path a real visitor takes — and, just as usefully, check url redirect behaviour you assumed was fine: that a moved page lands in one hop, that http and https don't disagree, and that the chain ends at the destination instead of one redirect short of it.