There are ten hindrances to enlightenment (shown below) and four stages of realization (enlightenment) based on how many hindrances have been eliminated and / or the degree to which they have been eliminated.
A Buddha is someone who is fully enlightened. A person who is fully enlightened, but not the Buddha of our time, is called an Arahant in Pali. Such a person has eradicated all ten hindrances to enlightenment:
- The belief in a permanent personality, ego
- Doubt, extreme skepticism
- Attachment to rites, rituals, and ceremonies
- Attachment to sense desires
- Ill-will, anger
- Craving for existence in the Form world (heavenly realms)
- Craving for existence in the Formless world (heavenly realms)
(from Anguttara Nikaya 10.13)
An anagami (non-returner) has completely eradicated the first five hindrances and never returns to earth or any other world system (planet, solar system). Such a person is reborn to a heavenly realm and attains enlightenment from there.
A sakadagami (once-returner) has eradicated the first three hindrances and greatly weakened the fourth and fifth; attachment to sense desires and ill-will. Such a person will be reborn to either the human or heavenly realm and will attain enlightenment there.
A sotapanna (stream-entrant) has eradicated the first three hindrances and will be reborn no more than seven more times and rebirth will either be as a human or a deva in a heavenly realm.