Octet rule is for the atom to have 8 valence electrons. Which means that is has 8 valence electrons. Because for most elements, they must have 8 valence electrons to be stable and "happy". So the atoms tend to have 8 valence electrons and are nonreactive because they do not need to bond to become stable.
Example of a element that has an octet:
Argon, which is in Noble Gases group.