The basis for existing classical computers is the binary digit, or bit, which can have a value of either 0 or 1. In a quantum computer, bits are replaced by qubits which are in a superposition of states partially 0 and partially 1. It is this superposition that allows calculations to be performed in parallel. Measuring the value of a qubit causes it to collapse into one of the two classical bits, 0 or 1. In a well-organised quantum computation, that should not happen until it becomes necessary to find out what one of the values actually is.(Economist.com | Quantum computers)

I still don’t understand, but it sounds interesting