A two-handled cup is used to rinse the hands, most familiarly before reciting the brachah (blessing) over bread or challah.  The Hebrew words “netilat yadayim” conclude the blessing that’s said immediately after rinsing the hands but before lifting the bread or challah and commencing the blessing. It’s therefore called a “netilat yadayim cup,” and really has no other use. The two handles are its only required feature. Those made of plastic, having a plain, functional design, are as valid for use as those that are ornately decorated and made from an expensive metal, like silver.
Why two handles?
It has to do with something called “ritual purity,” the Hebrew for which is “taharah” (cleanliness).
“Ritual purity” means being in a state that allows you to perform a religious rite. Before you rinse, your hands are “ritually impure.” It has nothing at all to do with sanitation. You could wash your hands with soap & water and dry them, but they’d still be in a state of “ritual impurity.” To purify them, they have to be rinsed (not actually “washed,” as we use that word these days) with water and concluded with a brachah (except at the seder).
A number of things can make you “impure.” This has nothing to do with “wrong,” “bad,” “evil,” etc. There’s a continuum of factors or conditions (see the link above), very few of which are irremediable.
In the typical procedure, each hand is rinsed separately. When you rinse your right hand, it becomes “pure.” To touch the same handle as the left hand (still impure) touched would make your right hand impure again. So, you hold the handle which has not yet been touched, and rinse the left hand. That’s why you need two handles to do this. Then conclude by saying the blessing “netilat yadayim.” Both hands are now “ritually pure.”
A specific section of the Talmud goes into this in greater detail: Seder Taharot, the 6th and final “seder” or major division of the Talmud, entitled “Cleanness,” within which is a subdivision (masechet) entitled “Yadayim” or “Hands.”
Torah mandates certain times at which someone who has become “unclean” returns to a state of “cleanliness” by a total immersion of the body. Kohanim — priests — had to wash their hands and feet before entering the Heichal (the outer room of the Mishkan and Temples) when making the sacrificial offerings. To no small degree, the halachot about rinsing our hands is based on the mitzvot of the kohanim — as if to suggest to us that we should each see ourselves as much in G-d’s Presence as a kohein entering the Temple (especially the Kadosh Kadoshim — the Holy of Holies, or innermost room of the Mishkan and Temples).
It’s one of the earliest areas of difference between rabbinic practices and those of Jesus, who regarded it as a “tradition of men”  — i.e. a requirement that was man-made, having no Divine authority. To an extent, he concurred here with the Zadokim (“Saducees”), who accepted the authority of the written Torah, but not that of the “oral” Torah accepted by the P’rushim (“Pharisees”). One might even say that from this seemingly insignificant difference, subsequently comes the entire separation of “Christian” tradition from its “Jewish” basis (especially in Paul’s later teachings on the role of Torah and mitzvot).
While “ritual purity” is one of the religious aspects that separated Judaism and Christianity, it’s one in which Islam closely resembles Judaism. In fact, the concept in Islam is called “taharah” — the same as in Hebrew.  The similarities between Muslim and Jewish “taharah” would make a very interesting study.
Hinduism likewise has a very developed tradition of “ritual purity” from the Vedas. My impression is that Buddhism, like Christianity, left off focusing on the “ritual purity” of its source-religion.
But just as “ritual purity” isn’t strictly synonymous with sanitation, neither is it strictly synonymous with “spiritual purity.” The latter I take to mean a state in which our perceptual experience of G-d’s Presence is more or less clear and immediate (allowing for differences of degree), as was Adam’s (and Eve’s) before their act of disobedience.
This is analogous to sunlight streaming through a window: If the window is clean, the light comes through unhindered; a fine layer of dust allows the light through, but with diminished intensity; an encrusted layer of grime can obscure the light completely, without negating the fact of the light itself. Our own negative thoughts and actions can be sources of such perceptual obstruction. “Teshuvah” or “Musar” can mean a positive change in our behavior, but leave the perceptual “dust” in place. A process of “cleansing” — “memarkin,” as Rabbi Joseph Soloveitchik and others call it — can be necessary to return us to a clearer spiritual perception that is our natural state; to “cleanse” our “window” or inner “mirror.” Many today find this through meditation.
Speaking subjectively, the “netilat yadayim” procedure helps me mark a cognitive transition from involvement in the mundane to involvement in the holy.
 For a fuller discussion, see:
 Mark 7:8
 For further discussion, see: