Higher worship is the worship of the creator of your race.
Higher worship is a form of worship based on an ingrained feeling that a turning point in your life is at hand and you need to return to your "roots".
Higher worship only appears in secondary or tertiary races, and only a portion of those races ever experience this pull to higher worship.
Another way to look at it is that the primary races always conduct a form of "higher worship" by proxy if they perform standard worship , since the first of their race is also the creator of their race.
Very very rarely, some member of a tertiary race wishes to worship even closer to their roots and thus feels the need to worship a primary god trough higher worship.
Higher worship is almost always temporary and after having "found oneself" the person usually returns to a form of standard worship.