A redirect chain is a URL that sends a reader through two or more hops before it lands on the final page. You ask for A, A redirects to B, B redirects to C, and only C is the real page.
Every hop costs. It is slower for a person, it spends crawl budget, and each redirect passes a little less equity than a direct link. Some crawlers give up after a few hops and never reach the destination.
Use a 301 for a permanent redirect, not a 302, so engines treat the destination as the real URL. Collapse chains so each old URL points straight to the final one, A to C, not A to B to C. Update your internal links to point at the final URL so nothing has to redirect at all. For a whole-site rule like www to non-www, or HTTP to HTTPS, set it once at the server, CDN or edge rather than per page.
Topkay follows redirects and shows the full chain with each status code, in the audit and the HTTP headers tool.