Hi all, I start to read some popular science on quantum physics. The term "entanglement" appears everywhere in quantum communication and other related fields. I am trying to understand this concept based on my undergraduate knowledge on physics. From some online resource, I have a feeling that an entangled system is a system of two or more particles under some interaction. An typical form of an entangled system I seen everywhere is something like ##|0\rangle \otimes |0\rangle + |1\rangle \otimes |1\rangle ## To my level, it looks like a system of a superposition of something. However, there is a weird math symbol ##\otimes## that confusing me. Could anyone explain in plain english what's above expression really stands for. And what's the difference between an entangle state and superposed state? Thanks.