Sitemap is a XML file where you have the list of the URLs in your website
Search engines can crawl your website because any page of your website can be accessed through a URL.
If you put the URL in your
sitemap.xml file SE can index the URL quickly.
url and lastmodified date is the most important for the search engine
You have two different types of sitemap
Users can view the sitemap of your website and they can navigate easily
There are five types of XML sitemap based on the type of the content.
This is the most common sitemap used in websites and you create the sitemap in XML format and add all URLs to the XML file.
XML sitemap has some limitations.
To avoid this limitation you can create index for sitemap ( XML index sitemap)
This is an index site map in a WordPress website and this site map has links to other sitemaps. Yoast SEO plug-in create separate sitemaps for posts, pages, and categories
XML image sitemap can direct Google to discover the all images hosted on your site. Although images are embedded inside of your webpage you can submit the image site map to Google.
You can use JSON-LD schema.org/ImageObject markup to create tags in XML image sitemap.
More details on image sitemap can be seen on Google search central – Image sitemap.
Sometimes this will waste your crawl budget so in some cases this is not mandatory to submit to Google.
You do not have put images in your server but you can use CDN.
XML video sitemap in WordPress can help Google to find the video content of your website
Having a sitemap is not a ranking factor