Tzitzit are four fringes, commanded by G-D to be worn as a reminder of the Mitzvot (the 613 commandments) you’ll find throughout the Torah. In Orthodox Judaism, special shirts are worn every day/all day with the tzitzit fringes, but they will also wear a special prayer shawl called a “Tallit,” during prayers, which also bare the tzitzit. The tzitzit is mentioned twice in the Torah;

And Hashem said to Moshe saying: Speak to the sons of Israel and say to them [that they must] make for themselves tzitzit upon the corners of the clothes for generations, and on the tzitzit give a string of techelet. And they shall have for themselves tzitzit and they will see them and they will remember all of the commandments of Hashem and they will do them, and they will not stray after their hearts and eyes so that they shall not pursue after them. So that they will remember and adhere to all of my commandments and will remain holy to their God. I am Hashem your God who took you out of the land of Egypt to be for you a God. I am Hashem your God.

— Numbers  15:37-41

You shall make tassels on the four corners of the garment with which you cover yourself.

—  Deuteronomy  22:12 
             Tallit example

In Reform Judaism, a tallit is not often required, nor are the fringes of the tzitzit, however, I choose to wear a tallit during my prayers, to set my mind more focused and to prepare my mind and spirit for communication with the holy. We don’t require others to wear them in the Reform movement, because in general, we allow spiritual autonomy in that individuals can be free to choose what brings them deeper spirituality and a connection with G-D. I personally find the Tallit rewarding and a deeply powerful tool in my prayers with, to, and for Hashem.