[konklone]

Second level domains. There are waayyyyy more subdomains, as you note. You can see some information and estimates on this here:

https://18f.gsa.gov/2017/01/04/tracking-the-us-governments-p...

We (18F, me) personally measured at least 26,000 (though some of these are used as redirects or are just error pages, etc.).