The more seriously one takes the mitzvot and the greater the weight one gives to their inward dimension, the more one will raise questions of how and why, questions of essence.
In a sense, the entire Torah can be seen as a set of explanations for the mitzvot, from the elucidation of how they are to be carried out to the study of their manifold meanings on a variety of planes.
The great principle of "we shall do and we shall hear" refers not only to the need to obey and the willingness to do so without hesitation.
The "we shall do" aspect of a given mitzvah is essentially quite simple and easily attainable, whereas the "we shall hear" part is almost infinite, just as the Torah itself is "broader than the earth" and inexhaustible.
In the study of Torah one can draw a distinction (of practical rather than intellectual consequence) between investigation that is directly related to the performance of the mitzvah at hand, and that which is unrelated.
In other words, each mitzvah is expostulated according to commentary and rabbinic tradition (midrash halakhah) concerning the Torah-text, on the one hand, and according to the details of what, when, and how (practical halakhah), on the other.
But there is yet a third body of inquiry: concerning kavannah (intention), that which gives subjective meaning to the mitzvah in the mind of the doer at the moment when he carries it out.
–Rabbi Adin Steinsaltz
From "Actions and Intentions" in Teshuvah: A Guide for the Newly Observant Jew by Rabbi Adin Steinsaltz