In the times of the sages, it used to be that men would wear their
large Tallit garments everywhere, but the difficulty of keeping your thoughts 100% pure when wearing them, as well as the prohibition to wear the tallit in the bathroom eventually inspired the Jewish people to create another way to wear their fringes that was more casual and easier to wear in day-to-day life: the
Tallit Katan (small tallit). Both smaller in size and featuring less strict rules, this garment is typically worn underneath the shirt (some communities wear it on top, however), and is sewn out of the required rectangular piece of fabric, Tzitzit fringes tied on each corner. In the center of the rectangle is a hole for the head, and some versions of the tallit katan are also sewn up on the sides, forming an undershirt with edges left loose to hold the fringes.

While there are rules regarding the way that the Tallit Katan's garment has to be made, the main function that it serves is holding the Tzitzit string fringes, as commanded in the scipture: "Speak unto the children of Israel, and bid them that they make them throughout their generations fringes in the corners of their garments, and that they put with the fringe of each corner a thread of blue. And it shall be a fringe for you, that ye may look upon it, and remember all the commandments of the LORD, and do them; and that ye seek not after your own heart and your own eyes, after which ye use to go a whoring: That ye may remember, and do all my commandments, and be holy unto your God." (Numbers 15:38-40) and "Thou shalt make thee twisted cords upon the four corners of thy covering, wherewith thou coverest thyself." (Deuteronomy 22:12)
Tzitzit fringes are themselves full of a myriad of traditions. You may want to wear them with Tchelet coloring or without (the argument for without is that the dye they use for this today may not be the dye intended to be used for the task), and there are also different styles of tying the knots of the fringe, and different lengths.
The fringe is what is actually called Tzitzit, but the entire tallit katan garment is often referred to as such. Different communities also pronounce the word ציצית differently. The biblical and Middle

Eastern (i.e. Mizrachi) pronunciation is something like ṣiṣit (pl. Ṣiṣiyot), while the Spanish and Mediterranean (i. e., Sephardic) jews pronounce it tzitzit; European and Yiddish (i. e., Ashkenazi) Jews saying tzitzis. Yemenite (i. e., Temani)Jews say ṣiṣith and the Samaritan pronunciation is ṣeṣet.
Orthodox Jews generally start donning the Tallit Katan daily from the tender age of 3, after the Upsherin or Chalakeh ceremony where the child gets his first haircut and shows his knowledge of the Hebrew alphabet, no longer then being considered a baby in Jewish law.
There are different sizes and different styles of Tallit Katan available; the garment part can be found in various types of cloth, the fringe with or without the blue Tchelet dye. This item of Judaica clothing is a central and fundemental part of Jewish life.