I'm curious how something like squarespace or lighcms or wordpress work from a code-base standpoint. What I mean is, a single code-base and single database drives multiple websites with their own domain names. So if you, the developer, ever had to update the code, you only had to update one central code-base, and all websites would immediately be updated too. Is it as simple as the code reads the HTTP request and spits out the proper website based on the domain name in the request? Or is it more complicated than that? If so, how is it done or where can we learn more?