From a name to a server: DNS

One loose end. You type shop.example.com, but computers don't actually find each other by name — they use numeric IP addresses like 203.0.113.42. DNS (the Domain Name System) is the web's phone book: before your browser can send a request, it quietly asks DNS to translate the friendly domain name into the numeric address, then connects to that. You buy a domain, point its DNS records at the server running your app, and from then on the name leads people to your machine. It's a lookup step you'll almost never see, but it's why a memorable name can stand in for a string of numbers.