T is the twentieth letter in the alphabet. The modern T hails from the Phoenician letter 'Taw'. It has retained its basic shape fairly well over the ages. It is the second most common letter in the alphabet and is the most common consonant.
The letter T can have a long or a short sound, depending on the other letters surrounding it. It can also have a Th sound when a H is added afterwards. This can sometimes be added into other words such as turning Ere into There.
T is the most common consonant in the English language, and is hence well represented in the Scrabble letter pouch with six T-tiles. It is a minimum score letter yielding only 1 point, but since is so common in the language it is a handy letter often needed to form big words with other higher scored letters.
It is not generally worth using the letter T on any bonus tiles, where you can avoid it because you will not get the best points for it. T is one of the safest letters to have left over in the end, since it is less likely to cause too many problems, and very easy to place next to already laying tiles to make new short words.