A network of networks
The internet is not a single network. It is a global system of interconnected networks — run by ISPs, companies, universities and governments — that communicate using common protocols. The key protocol suite is TCP/IP: the Transmission Control Protocol and Internet Protocol, which define how data is packaged, addressed and routed.
DNS: the phone book of the internet
When you type a web address, your computer first needs to find the IP address (a numerical identifier like 142.250.180.14) of the server hosting that site. This lookup happens through the Domain Name System (DNS) — a distributed, hierarchical database that maps domain names to IP addresses. Your request is typically resolved in milliseconds.
How a web page loads
Once your device knows the IP address of the server, it establishes a TCP connection (a three-way handshake: SYN, SYN-ACK, ACK). It then sends an HTTP or HTTPS request. The server processes the request and sends back a response — the HTML, CSS, JavaScript and images that make up the page. Your browser assembles these into what you see on screen.
Why HTTPS matters
HTTP transfers data in plain text. HTTPS (HTTP Secure) encrypts the connection using TLS (Transport Layer Security), which prevents anyone between your device and the server from reading or altering the data. The padlock in your browser indicates an HTTPS connection. Modern browsers warn when sites use plain HTTP.