Whether the site is up, and how quickly it responded
Checks whether the server is reachable, what status code it returns, and how long it took to answer. That time splits into finding the server in DNS, connecting, the TLS handshake, waiting for the server, then downloading the page.
A baseline. If this one fails, most of the other checks are measuring nothing.
Certificate issuer, validity dates and the chain of trust
Every HTTP response header the server sends back
Lighthouse scores for performance, accessibility, SEO and best practice
Where in the world the server is physically hosted
Other hostnames Shodan has seen on the same IP address
The full chain of redirects before the final page loads