Worked example: You send a 1 MB photo over 4G. How is it carried? Step 1: The phone digitises and compresses the photo, then TCP chops it into packets of about 1,500 bytes: 1,000,000 / 1,500 ≈ 667 packets. Step 2: Each packet gets an IP header with your phone's address and the destination server's address. Step 3: The packets ride the radio link to the nearest tower (a few km), are handed to fibre, and routers forward them across the internet — different packets may take different routes. Step 4: TCP at the server reorders them, requests re-sends of any lost packets, and rebuilds the exact photo. Conclusion: even a single photo is hundreds of independent packets finding their own way — the packet-switching idea in action.