What it is
Quantum networking seeks to distribute entanglement or quantum states across distance. The three uses, in rough order of arrival: quantum key distribution (measuring a quantum signal disturbs it, so an eavesdropper sets off the alarm by listening. The principle behind China's roughly 2,000-km Beijing–Shanghai backbone and the Micius satellite), networked quantum sensors (clock networks, distributed telescopes), and eventually distributed quantum computing: linking modules into bigger machines.
Why it's hard
Repeaters, memory, loss, interfaces, and standards remain the major hurdles. Unknown quantum states can't be copied (no-cloning), so a quantum repeater can't just re-amplify a signal the way classical fiber does. It has to work by entanglement swapping and purification, which needs quantum memories that don't exist at scale yet.
And the standing correction: entanglement does not allow faster-than-light messaging. Any usable information still obeys the ordinary limits of communication.
Deeper treatment
Repeater architectures, memory requirements and interface engineering are covered in the advanced Academy module Quantum Security, Networking, and Sensing.