Quantum teleportation, also known as "entanglement," is a method for transmitting information over distance faster than the speed of light allows for conventional communication. The technique is far from having been perfected as of August 2014, and it involves little-understood features of the way subatomic particles relate to each other across space and time.
To teleport information, it is necessary first to entangle two particles so that the spin of one is always the opposite of the other. This is done by allowing one subatomic particle to decay into two daughter particles. If the original particle had a quantum spin of 0, the daughter particles must have a combined spin of 0. One particle can have a spin of 1/2, and the other can have a spin of negative 1/2. In this sense, the two particles are entangled, and anything that affects the spin of one necessarily affects the spin of the other.
This phenomenon resembles what Einstein called "spooky action at a distance" when the two particles are separated and the spin of one particle is measured. This instantly collapses the uncertainty over the second particle's spin, effectively transmitting information to the second particle infinitely faster than light could carry a message. In theory, if the spin of the first particle could be manipulated, the second particle could be affected without the need to communicate with the source in any conventional sense. Although only particles and single atoms have been teleported, there appears to be no size limit to the objects that can be entangled in this way.