Every one means the same as each one.  When Tiny Tim says "God bless us, every one!" the meaning is clear.   When someone says go through these books, every one should be checked for bugs, it means: not a single book should be left out. 

Everyone means everybody.  This word only applies to people; like everyone thinks you're so innocent!  The implication is that 'But I know what a crook you really are.'

Also desert, place with a lot of sand, and dessert, something sweet, to eat after the main course.  Desert can also be a verb, too heedlessly abandon some person, or some duty.