The term “web server” has two meanings. One is the physical (or virtual) server than contains the website’s files and such.
The other, and the one this page is about, is the service that accepts HTTP requests from a browser, and responds with the appropriate files such that the browser can display the webpage it requested.
Historically, there have been two main web server services: Nginx and Apache HTTP Server. These are both still used today due to their high configurability and speed. Nginx can also be used as a reverse proxy to allow for one server to host multiple websites – see Proxies for more.
I, however, use Caddy, an up and coming open source web server that can act as a reverse proxy and automatically provides you with certificates so you don’t need to use certbot to do so.