"Everyone" and "every one" have similar roles to play in the English language, but these roles aren't exactly the same. "Everyone" always refers to human beings, while "every one" could refer to the members of a group of any type of thing.
How to Use "Everyone"
The word "everyone" is an indefinite pronoun. That is to say, it is a pronoun that refers to an indefinite group of people. "Everyone" (one word) is a synonym for "everybody" (although "everybody" is slightly less formal), and it means all the people, every person, as in "Sooner or later, everyone goes to the zoo." "Everyone" always refers to people, to humans, or to humanity in general.
How to Use "Every One"
The phrase "every one" (which combines a modifier and a noun) is more explicit, referring to each individual or thing in a particular group, as in "Every one of our friends has gone to the zoo." "Every one" is usually followed by the preposition "of." In practice, "every one" is a near synonym of "each one of a set," so it does not necessarily refer to people at all; therefore, you must state who or what you are referring to.
