The Tallit is a (usually) white prayer shawl worn over the head and shoulders of Jewish males at morning prayers. Fringes are affixed to the four corners of the shawl. A smaller version is worn under the clothes during waking hours by Jewish males. The larger, external shawl is worn in some communities only by married men and in others from the age of thirteen. The age of thirteen is considered the rite of passage for Jewish males into adulthood. The smaller version is worn from the age of three.
Apart from the aforementioned instances, grooms of Sephardic origin wear a Tallit under the wedding canopy. Some will use a Tallit as the actual wedding canopy.
The Tallit is also worn throughout the day of Yom Kippur (the Day of Atonement, the holiest Jewish day of the year).
When Jews are buried (G-d Willing after a full one-hundred-and-twenty years), they are dressed in a shroud and Tallit.
In the case of the smaller shawl that is worn throughout the day, one recites the following blessing before putting it on: "Blessed are you, Lord our G d, King of the universe, who has sanctified us with His commandments, and commanded us concerning the mitzvah of tzitzit."
- In the case of the larger shawl, it is put on before the morning prayers and the following blessing includes the smaller shawl, meaning if one recites the following blessing he should have the smaller shawl in mind too and will thereby have no need to make the previous blessing as well: "Blessed are you, Lord our G d, King of the universe, who has sanctified us with His commandments, and commanded us to enwrap ourselves with tzitzit."
There is a law (written in the Orach Hayim 16:1) that even the smallest Tallit should be large enough to clothe a child who is old enough to stand and walk.
If buying a Tallit for a Bar Mitzvah boy, it is advisable to buy a Tallit that will be appropriate for him also as an adult.
First and foremost, the purpose of the Tallit is simply to hold the tassels on the four corners. The tassels are to remind one on a daily basis and at every moment of G-d's commandments.
Having said that, there is no reason not to take advantage of the wide selection of Tallitot that are available on and off-line. There are Tallitot available in all different colours, in a variety of materials, with or without an intricately woven neckband. It is worth spending that extra money in order to beautify one's fulfilment of G-d's commandment.
Most importantly, be sure to purchase from a reliable source. Tallitot have many intricate laws and it is essential that one fulfil the commandment of wearing a Tallit while wearing a kosher one.