What a redirect chain is
A redirect chain happens when URL A redirects to B, and B redirects again to C. Chains usually build up over time: an http to https rule, then a www rule, then a URL restructure, each added separately. A redirect loop is a chain that points back to an earlier URL and never ends.
A typical example is http://example.com/page going to https://example.com/page, then to https://www.example.com/page, then to https://www.example.com/page/.
Why chains are a problem
Every hop is another round trip, which adds latency for visitors, especially on mobile. Googlebot follows up to 10 hops and then gives up, and long chains waste crawl activity that could be spent on real pages. Each extra hop is also another place where a misconfiguration can break the path.
Google passes signals through redirects, so a short chain rarely hurts rankings on its own, but flattening chains is cheap and makes every page faster.
How to fix a redirect chain
Change each old URL to redirect straight to the final destination in one 301. Combine host and protocol rules so http, https, www and non-www all reach the canonical URL in a single hop, then update internal links, canonical tags and the XML sitemap to point at final URLs so most visitors never hit a redirect at all.
Example
A three-hop chain and its fix:
Before:
http://example.com/page 301 -> https://example.com/page
https://example.com/page 301 -> https://www.example.com/page
https://www.example.com/page 301 -> https://www.example.com/page/
After:
http://example.com/page 301 -> https://www.example.com/page/