Introduction:
The part of the sheep and goat used to make wool is their hair. This hair is sheared or collected from the animals and then processed to create wool, which is used for various purposes, including making fabrics, clothing, and textiles.

Explanation:
Here is a detailed explanation of why the hair of sheep and goats is used to make wool:

1. Sheep and Goat Hair:
- Sheep and goats have a dense coat of hair that keeps them warm and protected in cold climates.
- This hair is made up of fibers called wool, which are naturally crimped and have insulating properties.
- The hair of sheep is commonly referred to as wool, while the hair of goats is known as mohair (from Angora goats) or cashmere (from Cashmere goats).

2. Shearing and Collection:
- To obtain wool, the hair of sheep and goats is sheared or collected.
- Shearing is the process of removing the entire fleece or wool from the sheep's body using electric clippers or manual shears.
- The collected wool is then sorted based on its quality, color, and length.

3. Processing and Manufacturing:
- The collected wool goes through a series of processes to make it suitable for various applications.
- The wool is scoured or washed to remove impurities like dirt, grease, and sweat.
- It is then carded, where the fibers are separated and aligned to prepare them for spinning.
- The carded wool can be spun into yarn, which is then used for knitting or weaving fabrics.
- Alternatively, the wool fibers can be processed further to create felt, which is a non-woven fabric made by matting the fibers together.

4. Uses of Wool:
- Wool is a versatile material with many uses.
- It is commonly used in the textile industry to make clothing, blankets, and upholstery.
- Wool fabrics are known for their warmth, breathability, and moisture-wicking properties.
- Wool is also used for insulation in buildings, as it has excellent thermal properties.
- Additionally, wool is used in the production of carpets, rugs, and felted products.

Conclusion:
In conclusion, the hair of sheep and goats is used to make wool. This hair is sheared or collected from the animals, processed, and then used for various purposes. Wool has many desirable properties, making it a valuable material in the textile industry and other applications.