1. each with two or more; every with three or more (both with singular nouns)
»»» The business makes less money each/ every year.
»»» She had a child holding on to each hand. (NOT every hand)
2. meaning
They can often be used without much difference of meaning.
»»» You look more beautiful each/ every time I see you.
But when we are thinking of people or things separately one at a time, each is preferred. And every is more common when we are thinking of people or things together, in a group. (every is closer to all.)
»»» Each person in turn went to see the doctor.
»»» Every patient came from the same small village.
3. structure
We do not use each with words and expressions like almost, practically, or nearly which stress the idea of a whole group.
»»» She's lost nearly every friend she had. (NOT nearly each friend...)
Each can be used in some structures where every is impossible.
»»» They each said what they thought.
»»» Each of them spoke for five minutes.