The first eighteen centuries of Rabbinic Judaism were simply called Judaism. About two centuries ago, when Reform Judaism came into being, traditional Jews began to call themselves “Orthodox,” to distinguish themselves as faithful to Mosaic tradition.
Orthodox Jews believe that the Torah is of divine origin, the exact word of God, without any human influence. Orthodox Jews do not accept historical-critical scholarship as Conservative Jews do, so even their rabbinic (man-made) law changes very slowly.
You shall love the Lord your God with all your heart, and with all your soul, and with all your might. And these words which I command you this day shall be upon your heart; and you shall teach them diligently to your children, and shall talk of them when you sit in your house, and when you walk by the way, and when you lie down, and when you rise. And you shall bind them as a sign upon your hand, and they shall be as frontlets between your eyes. And you shall write them on the doorposts of your house and on your gates Deut 6:5–9.
Hasidic Judaism is an Orthodox Jewish movement started by eighteenth century Jewish spiritual masters, emphasizing that God is omnipresent and always in communion with us. Hasid comes from the Hebrew khasidut, piety, which in turn comes from the root khesed, grace-enabled loving kindness in charitable acts. Pre-Christian Hasidim were fiercely devoted to the Torah.