Today's Enneagram personality types evolved in large part from five of Oscar Ichazo's enneagrams: the Enneagram of Fixations, Holy Ideas, Traps, Passions, and Virtues.
Ichazo identified nine ways in which ego becomes mentally fixated. One of these fixations will be dominant for each person. Each fixation is indicated by a label assigned to a different number on the Enneagram of Fixations (e.g., the fixation for type 1 is resentment).
Each ego fixation is remedied by a holy idea. For example, resentment at point 1 on the Enneagram of Fixations is remedied by holy perfection at point 1 on the Enneagram of Holy Ideas. The holy idea represents something lost when the ego created a sense of separateness between the self and the world.
The ego trap, found on the Enneagram of Traps, is the mistaken remedy for resolving the fixation. Whereas the holy idea resolves or alleviates the fixation, the trap only reinforces the fixation. In other words, the trap perpetuates the fixation and keeps an individual stuck in ego. Looking at type 1, the trap of perfection takes the individual's sense of perfection and attempts to impose it upon the world as an absolute truth with the individual often unaware that it's only the individual's egoic interpretation of how things should be.
The passion can be thought of as an emotional energy that reinforces the fixation and trap of each type. For example, type 1 is working toward perfection and resents when people are not working toward that end as well. The passion of anger arises as an energy that pushes toward perfection by way of criticism, correction, discipline, etc.
A person caught up in the fixation and trap will lose touch with the corresponding virtue because the passion gets in the way. The way to the virtue is through reducing or eliminating the passion. The way to reducing the passion is by finding some freedom from the fixation and trap.
Looking at type 1 as an example, the virtue is serenity. The energy of anger can be reduced by finding some freedom from the fixation and trap of resentment and perfection. Serenity begins to appear as a natural byproduct when the energy of anger is no longer getting in the way of it.