Well, you know the expression "each and every" so I suppose each refers to one thing and every something else and together they mean all. I frankly can't tell you that there's some complex grammatical difference, but if there is, it's a fairly trivial one to worry about. I can think of examples where the words are synonymous. Imagine a pearl neckless. You could say "every pearl on the neckless is white" or you could say "each pearl on the neckless is white" and the words mean the same thing.

From a stackexchange thread: "Each is used for the individual person or item, and the focus is on the individual, not the group. Every is also used for the individual, although the focus is shifted to the group."

Hi WilliamVZ, Well they both can describe a single unit. Each day = every day, as Steven mentions. I would like to add a difference in the usage. "each" can be used as a pronoun to refer to a thing or a person, but "every" can just be a adjective. Each of the cards has a pattern. (correct) Every of the cards has a pattern. (wrong) Every one of the cards has a pattern. (correct) Each one of the cards has a pattern. (correct) Hopefully this helps. :)