I'd like to know what the specifications of the server (Web, DB) are actually using in the field.

As the title suggests, I'm asking if there are many companies that build and use web servers or DB servers separately based on startups or small and medium-sized enterprises, or operate webs and DBs on one server, and what are the actual hardware specifications?

I'm curious about the specifications of hosting if you don't buy the server directly and use it.