Can you tell why someone would be interested in these kind of codes?
We have seen n=9 physical qubits have been used to encode 1 logical qubit. This seems like a waste of qubits, but it is not. What is the advantage in the long term?
As it has been mentioned shortly in the video, surface codes are useful to detect errors and correct them. This way, n physical qubits are used to encode k logical qubits that are more robust against errors in the system.
These codes are widely used in superconducting qubits, for example, and varius shapes are implemented.