What is the significance of the Tibetan terms "Rinpoche, or Rinpoche La," "Tulku, or Tulku La," "Khenpo, or Khenpo La"?
Tulku and Khenpo are titles with special significance. Tulku is the title exclusively for the rebirths of deceased high lamas, as we have discussed. Khenpo is the title exclusively for the senior monks and the heads of the monastic communities who have been ordained for ten yeasr or more and are observing monastic rules, including celibacy.
Rinpoche means "the Precious One." It is one of the highest honorific terms that you can find in Tibetan, and is used for addressing the highest lamas. You can use rinpoche by adding it after the titles of the lamas or using it independently, as Tulku Rinpoche for tulkus, Khen Rinpoche for khenpos, or just Rinpoche for both.
When it comes to using "La," you must consider the geographical background of the person you are addressing. If they are from Central Tibet and if they are equal to you or only a little higher than you, then you add "La" after the title — for example, Tulku La or Khenpo La. If they are higher than you, you should not use "La," but address them as Tulku Rinpoche or just Rinpoche, Khen Rinpoche or just Rinpoche. So, keep in mind, that if you are addressing a tulku, khenpo, or rinpoche who is higher than you and if you add "La" after their titles, it may come across as patronizing.
If they are from Kham or Amdo provinces, you don't add "La" at all after their titles or names. You just addresss them as Tulku, Khenpo, or Rinpoche.