Website Analysis section is made up of two tools: Domain Analysis (including or excluding subdomains) and URL Analysis. The former becomes active when you enter a domain's address into the search bar on Serpstat (without http/https), while the latter becomes accessible upon entering a URL address (including http/https). If you intend to research the domain's main page, please make sure to type in the full URL with http/https.
You can research the whole website category as well. Enter the category address into the search bar on Serpstat, select URL Prefix as a regular expression and click on Search. The platform will return a list of pages that belong to the category along with keywords they're ranking for.