Quantum computing is a strange beast
that still uses 1s and 0s, but allows both states to exist at the same time (time
was, we'd throw that data away!). Instead of "bits," we have "qubits." Qubits can
exist in superposition, and groups of qubits can be "entangled." Entanglement is
a sort of long-distance sympathetic relationship between separated pairs of qubits.
The important aspect of quantum computing is how much faster numbers can be crunched.
For example, a classical computer (like the one you are using now) requires around
5x10^24 steps to find all the prime factors of a 300 digit number, or about 150,000
years at a terahertz speed. A quantum computer could accomplish the task in a just
5x10^10 steps, which is less than a second at terahertz speed. That means today's
best encryption algorithms could be cracked in less than a second.