It's larger than Christianity, it's religion at large. Religions, even organized ones, aren't as organized as you're led to expect.

Religions are amalgamous. You're asking about the theology of the monks and how the layman's faith relates to that. That reaches across the layers, and while there are some attempted answers, I don't think you'll find them satisfactory or clear. In any case, you would have to learn some theology to understand them

For example, everyone knows that Buddhism is about nirvana, but in truth that is only expected for the most dedicated monks ready to give up their lives in an instant, not the laymen who are actually only expected to live moral lives, not even caring about nirvana until a future life when they're ready for it