There are principally two types of sitemaps:
+HTML sitemap (written in Hypertext Markup Language)
+XML sitemap (written in Extensible Markup Language)
XML Sitemaps can have two types.
+Index Sitemap (how many URL sitemaps a website have)
+URL Sitemap (contain final information of URLs on webpage)
XML sitemaps are further divided into 3 different categories.
+ Sitemaps for webpages (commonly known as xml sitemap in community)
+ Image sitemaps (details of images and their URLs on website)
+ Video sitemaps (what webpages have videos embedded in them and their details)
So, final tree of sitemaps categorization we have is;
+XML Sitemap
+Index Sitemap
+URL Sitemap
+ Sitemaps for Webpages
+Sitemaps for Images
+Sitemaps for videos
+HTML Sitemaps