When HaShem came to B'nei Yisrael and offered them the Torah, we collectively answered unequivocally in the affirmative. This response is documented twice: in parshios Yisro (Shemos 19:8) and Mishpatim (24:7). (It's actually mentioned twice in Mishpatim so technically, it's three in total.) The common text found in both locations is "kol asher diber HaShem na'aseh," we will do all that HaShem has stated. Meshech Chachmah raises a very simple issue with this statement. It is impossible for any one person to actually do all 613 mitzvos. Some apply only to kohanim. Some apply only to men, some only to women. What then is meant by that statement?
This question is answered in two different ways, based on the different variations of the response. In Yisro, it is stated, "the entire nation responded together." Although no one member of klal Yisrael can perform all 613 mitzvos, together as a unit we can cover the gamut. In Mishpatim, we have the extra word "venishma." We will do and we will listen. The term shemiyah is often associated with learning. The mitzvos that we are not able to actually perform, we can supplement with the actual studying of the laws pertaining to those mitzvos.
This understanding of this fateful moment in our history gives focus to two important aspects that we must keep in mind on Shavuos: the focus on learning the Torah as well as performing it, and the realization that we are all in this together and only if we function as a single unit, k'ish echad b'leiv echad, can we truly realize the Torah's complete purpose.
Have a chag samei'ach!