Everyone and every one are commonly confused and they have two very different meanings. Everyone is used as a pronoun to refer to all, whereas every one as a noun to refer to each individual.
Everyone
Use everyone as a pronoun to mean all the people in a group.
Examples:
Do you think everyone will want to come to the party?
She wants everyone to leave comments on her blog.
Every one
Use every one as a noun to indicate each person.
Examples:
Every one of the students has a question about the grammar.
My boss told every one of the employees himself.