"Ma'at" (mah-'-ot with the ' signifying a glottal stop) doesn't translate adequately into English. The best definition is an amalgam of words, ranging from "truth" to "harmony" to "stability", and the best correlation to Ma'at we can think of outside Kemet is the Taoist understanding of Tao, "The Way". Ma'at is what is right -- what is correct. When your life is in Ma'at, you can feel it.
Ma'at is also a goddess, usually pictured with a white ostrich feather in a band on Her head. She is perhaps one of the most abstract and all-pervasive subjects in Kemetic Orthodoxy, and an intricate part of the concept of Netjer.