Carpet padding, also known as underlayment or cushion, is a layer of material that is placed beneath a carpet to provide additional support, insulation, and comfort. It serves several important functions:

1. Cushioning: Carpet padding adds a layer of cushioning under the carpet, which makes the carpet more comfortable to walk or sit on. It helps to absorb impact and makes the carpet feel softer.
2. Insulation: It provides thermal insulation, helping to retain heat in a room and making it feel warmer. Additionally, it can help to reduce sound transmission between floors in multi-story buildings.
3. Extended Carpet Life: A good quality carpet pad can help extend the life of the carpet by absorbing some of the wear and tear that would otherwise be absorbed by the carpet fibers.
4. Reduction of Noise: It helps to dampen sound, making rooms quieter by absorbing noise from footsteps and other activities.
5. Prevention of Carpet Wrinkling: A proper carpet pad helps to prevent the carpet from wrinkling, bunching, or forming lumps over time.

Carpet padding comes in various materials and densities. Common materials include foam, rubber, fiber, and felt. The density and thickness of the padding can vary, and choosing the right type of padding depends on factors like the type of carpet, the level of foot traffic in the area, and the subfloor material.

When installing carpet, it's important to choose an appropriate padding that complements the carpet and provides the desired level of comfort and support. The right combination of carpet and padding can significantly enhance the overall feel and performance of your flooring.