If you’ve ever paid electronically, you’ve used encryption. Encryption is based on large numbers that are the result of the multiplication of prime numbers. A classical computer takes a very long time to reverse that multiplication (or ‘factor’) to get the prime numbers back, which is why encryption is safe. But a quantum computer can factor much faster, and thus break encryption!
We have seen that when there’s errors in the system, it can take a lot more qubits to encode information. How do you think this affects Shor’s algorithm?