https://www.sciencedaily.com/terms/quantum_entanglement.htm
Quantum entanglement is a quantum mechanical phenomenon in which the quantum states of two or more objects have to be described with reference to each other, even though the individual objects may be spatially separated.
This leads to correlations between observable physical properties of the systems.
For example, it is possible to prepare two particles in a single quantum state such that when one is observed to be spin-up, the other one will always be observed to be spin-down and vice versa, this despite the fact that it is impossible to predict, according to quantum mechanics, which set of measurements will be observed.
As a result, measurements performed on one system seem to be instantaneously influencing other systems entangled with it.
But quantum entanglement does not enable the transmission of classical information faster than the speed of light.
Quantum entanglement has applications in the emerging technologies of quantum computing and quantum cryptography, and has been used to realize quantum teleportation experimentally.
At the same time, it prompts some of the more philosophically oriented discussions concerning quantum theory.
http://www.nytimes.com/2014/11/16/opinion/sunday/is-quantum-entanglement-real.html
The key word is “instantaneously.” The entangled particles could be separated across the galaxy, and somehow, according to quantum theory, measurements on one particle should affect the behavior of the far-off twin faster than light could have traveled between them.
Entanglement insults our intuitions about how the world could possibly work. Albert Einstein sneered that if the equations of quantum theory predicted such nonsense, so much the worse for quantum theory. “Spooky actions at a distance,” he huffed to a colleague in 1948.
In his article, Bell demonstrated that quantum theory requiresentanglement; the strange connectedness is an inescapable feature of the equations. But Bell’s proof didn’t show that nature behaved that way, only that physicists’ equations did. The question remained: Does quantum entanglement occur in the world?
http://physics.about.com/od/quantumphysics/f/QuantumEntanglement.htm
The Wavefunction of the Universe
One way of interpreting things is to consider the entire universe as one single wavefunction. In this representation, this “wavefunction of the universe” would contain a term that defines the quantum state of each and every particle. It is this approach that leaves open the door for claims that “everything is connected,” which often gets manipulated (either intentionally or through honest confusion) to end up with things like the physics errors in The Secret.
Though this interpretation does mean that the quantum state of every particle in the universe affects the wavefunction of every other particle, it does so in a way that is only mathematical. There is really no sort of experiment which could ever – even in principle – discover the effect in one place showing up in another location.
Practical Applications of Quantum Entanglement
Although quantum entanglement seems like bizarre science fiction, there are already practical applications of the concept. It is being used for deep-space communications and cryptography. For example, NASA’s Lunar Atmosphere Dust and Environment Explorer (LADEE) demonstrated how quantum entanglement could be used to upload and download information between the spacecraft and a ground-based receiver.
http://www.livescience.com/28550-how-quantum-entanglement-works-infographic.html
