“Ngöndro” is a Tibetan word that means “going before.”1 In everyday language, it can mean “pioneer,” for example. In its technical religious meaning, it refers to sets of preliminary practices.
The job of a ngondro is to get you ready to practice a corresponding Buddhist system—that is, a particular yana. “Yana” literally means “vehicle.” A yana takes you from a starting point (called its base) to a destination (the result) using a collection of methods (the path). To begin to practice a yana, you have to be at its starting point. This is not a matter of bureaucratic box-ticking requirements; it’s a matter of functional capacity. If you don’t know basic algebra, you can’t start learning calculus; it would be meaningless to try. None of it would make any sense and you wouldn’t get anywhere. So highschool algebra class is the ngöndro for calculus, one might say.