Entanglement is one of the trickier elements of quantum mechanics to explain, and even harder to fully understand. By 'entangling' two particles to one another you are in essence binding their existences together, so that one is dependant on the other. It can be thought of as a symbiotic relationship between two co-species, whatever happens to one will affect the other. Entanglement however, does not require the two particles to be physically touching, or anywhere near one another, they are bound through their wave function.
The easiest way I found to understand this was making spaghetti bolognese. Once you mix the pasta into the bolognese, the two ingredients have become entangled and you can't add seasonings or garnishes to one without affecting the other.
Without rambling on too much, watch the video; its a great informative piece and may even change the way you think!