The Four Paths or Four Stages of Enlightenment are an organizing structure that is part of Theraveda teachings.  The first path is stream-entry.  The second path is a once-returner.  The third path is a non-returner and the fourth path is an arahant or enlightened person.

Sometimes people consider obtainment of first path, “enlightenment”, so you have to watch your terms.  This distinction is used because people that have reached first path cannot be reborn in any lower realm (hell, hungry ghosts, animal) and have insight into reality that clearly sets them apart from ordinary humans.

The technical attributes of the different stages have to do with removal of specific limitations.  The limitations that fall away at each stage and consequently define that stage are referred to as fetters.

The ten fetters are:

1. view that one is a separate self
2. belief that rites and rituals alone could lead to liberation
3. doubt or uncertainty, especially about the teachings regarding liberation (i.e. the eightfold noble path)
4. sensual desire
5. ill will
6. craving for material existence
7. craving for existence in the formlessness realm
8. conceit
9. restlessness
10. ignorance

The first three fetters are eliminated when one reaches the first path (stream-entry or aryahood).  Someone that has reached second path has significantly weakened the next two fetters as well as eliminated the first three.  A non-returner (third path) person has eliminated the first five fetters.  Elimination of the last five fetters results in enlightenment or obtaining fourth path (arhat).