Why is a sitemap relevant?

According to WCAG success criteria 2.4.5 (Multiple Ways - Level AA), users should be able to reach all subpages of a website in at least two ways (apart from very small websites with subpages that are all linked directly from the homepage). In addition to making them accessible via navigation menus, a sitemap that lists all the website subpages in a structured way and ensures further accessibility is also helpful. This can fulfill the above-mentioned success criterion.