DNS

DNS is the internet’s phone book: it turns a name like example.com into the numeric IP address computers actually use to connect. Your computer asks a resolver (usually run by your ISP or a service like 1.1.1.1), and if it doesn’t already know the answer it works down the hierarchy: a root server points it to the servers for .com, which point it to the domain’s own authoritative server, which gives the real answer. Every answer comes with a TTL, a time-to-live saying how long it may be cached, which is why lookups are usually instant and also why a changed record can take a while to reach everyone.