What is Rhythm and how does the temporal dimension of music evolve? How we can conceptualize the human Musical time feeling? How can we Count fast enough to understand the inner relations of different rhythmic patterns?
The main concept in modern Western rhythmic tradition is the Meters differentiation. While there's a plenty of other national musical time organisation systems, that may emphasize some other aspects of the temporal music feel, such as Syncopation, swing and groove.
And there's so much to explore in practice while learning basic Drum rudiments on your own.