The Enneagram is a symbol that's commonly used to represent nine personality types where each type is represented by one of the nine numbers on the symbol. You determine your Enneagram type by finding the type that best fits.
In addition to your Enneagram type, several concepts are often used with the types to describe subtypes or variations of type leading to more subtle distinctions for your type.
The self-preservation (sp), sexual (sx), and social (so) instincts create three variations or subtypes of each type.
The instincts can also used on their own in what can be called instinctual preferences, variants, or stacking. This approach can be used independent of Enneagram type to point out how two people can have both similarities and differences regardless of their Enneagram type.
Tritype sees a person in terms of three Enneagram types: one type from each of the three centers of intelligence. You still have a dominant Enneagram type but two other types from the two other centers influence and create a variation of your dominant type.