The Tày people speak a language of the Central Tai language group, and live in northern Vietnam. They are sometimes also called Thô, T'o, Tai Tho, Ngan, Phen, Thu Lao, or Pa Di.
There are about 1.5 million Tày people living in Vietnam. This makes them the second largest ethnic group in Vietnam after the majority Viet ethnic group. Most are in northern Vietnam in particular in the Cao Bằng, Lạng Sơn, Bắc Kạn, Thái Nguyên, and Quảng Ninh Provinces, where they live along the valleys and the lower slopes of the mountains. They also live in some regions of the Bắc Ninh and Bắc Giang provinces. They inhabit the fertile plains and are generally agriculturalists, mainly cultivating rice. They also cultivate maize, and sweet potato among other things.
Tày villages are usually based at the feet of mountains and are often named after a mountain, field or river. Each village has about 15-20 households.
The Tày are closely related to the Nung and the Zhuang on the Chinese side of the Vietnamese-Chinese border.
It is common for Tày woman to wear skirts or sarongs which go down to the knee, and are split up the right side with five buttons along the armpit and narrow sleeves.
Tày songs include the “Lượn”, which is a kind of duet between lovers and a kind of poem.
The Tay people speak the Tày language, among other Tai dialects. Literacy in their own language is quite low among Tày people, probably around 5% or less. Dialects include Central Tày, Eastern Tày, Southern Tày, Northern Tày, Tày Trung Khanh, Thu Lao, and Tày Bao Lac. There is a continuum of dialects to southern Zhuang in China.

 (Source: Wikipedia)