What is tritype theory?

Tritype theory explains that we have 3 enneagram types, one in each center, instead of just one type. In tritypes, we have a core type, and then we have the two other types which are used in a preferential stacking order. This theory is by Katherine Fauvre.

For example, if one's tritype is 296, 2 would be their core type, and then they would fall back on 9 and then finally 6.

Here is the link to Katherine Fauvre's tritype test

Here is an example of a tritype. 478, the messenger.

Sadly, I don't think that there is much information about tritypes online, so I apologize if this page is scarce.