The foundation of Judaism is that there is a G-d, who is completely spiritual. G-d created both a physical and spiritual world. The centerpiece of creation is man who is composed of a physical body and a spiritual soul. Our collective purpose is to transform the world into a unified G-d connected spiritual world.
To accomplish this spiritual transformation G-d transmitted the necessary knowledge and tools in the form of the Torah. The Torah informs us how to turn physical acts into G-d connected spiritual acts. Every positive act we perform can be G-d connected, but the ones with the greatest connection power are the mitzvos G-d explicitly specified in the Torah.
The holiday of Shavuos is the day that G-d spiritually transmitted the Torah. The entire Jewish nation experienced this transmission and Moses experienced it to a much greater degree. The day is filled with a spiritual energy through which we can deepen our commitment to connect to G-d through the learning of Torah.
On Shavuos and other Jewish Holidays (Passover, Succos), there is a mitzvah to enhance the joy of the holiday with one special meal at night and one special meal during the day. In doing so we transform the physical act of eating into a spiritual G-d connected activity.