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Routing is how packets move between networks: each router holds a table of known destinations and the next hop toward each, learned by configuration or by a protocol, and forwards each packet to the most specific match.

Switching is the forwarding of frames within a single network segment by a device that learns which hardware address sits on which port and sends each frame only where it needs to go.

A VLAN divides one physical switched network into several logical segments, each with its own broadcast domain, by tagging frames with a VLAN identifier so that ports and devices in different VLANs cannot reach each other without a router.

A CDN is a worldwide network of servers that answers requests for your site from a location near the person asking, instead of sending every request back to the single machine your site runs on.

DNS is the distributed lookup system that turns a hostname such as getting-digital.net into the IP address a browser can connect to, by walking a chain of nameservers whose answers are then cached for a lifetime the domain's owner publishes.

SSL/TLS is the protocol that encrypts the connection between a browser and a server and, by way of a certificate signed by a certificate authority, proves the server is entitled to answer for the domain in the address bar.