Each is used for one or two individuals or items, while every is used for groups. Each is used when you are emphasizing the individual person or thing.
Example: He paid $1 for each apple. In this case you wouldn't say every apple because you are specifically talking about specific apples.
It's confusing because you can use each and every interchangeably sometimes, but not always. You can even use them both together for emphasis.
Example: Each and every day you drive me crazy!
With the above sentence you could also say - Every day you drive me crazy. If I said, Each day you drive me crazy, it would put more emphasis on the each day part.
This may help more than I can.... http://www.englishleap.com/common-mistakes/each-every