Intimacy: Feelings of attachment, closeness, typified by sharing secrets, etc.
Passion: Feelings of sexual and romantic attraction.
Commitment: A willingness in the short-term to create and maintain a relationship and long-term plans to sustain the relationship.
Of course, a “perfect” relationship in Sternberg’s view contains all three components, but the various combinations of these psychological aspects of love create eight separate permutations that cover almost all relationships.