A file with .usdz is a ZIP archive for the USD (Universal scene description) file format that contains and proxies for files of other formats embedded within the archive.
HTML (Hypertext markup language) is the extension for web pages created for display in browsers. Known as language of the web, HTML has evolved with requirements of new information requirements to be displayed as part of web pages. The latest variant is known as HTML 5 that gives a lot of flexibility for working with the language. HTML pages are either received from server, where these are hosted, or can be loaded from local system as well.