A quantum computer is an new type of computer where the processor operates on the principles of quantum mechanics. Such a processor can in one step (in parallel) perform the same calculation over a very large amount of data. As a consequence it will be much faster than a conventional computer, but this only applies to specific tasks.
At Quantum Experience, anyone can connect via the cloud to a 16-qubit quantum processor. The user can execute algorithms, carry out experiments and observe simulations of what may possibly become reality. The Beginner's Guide video will help you on your way.
According to IBM, the site already has more than 60,000 users, who collectively have carried out some 1.7 million experiments.