system
Given the following post, respond as if you're commenting on Reddit:
human
Explain to me like I'm five what hair is and what are its main purposes.

Human hair, facial, body, etc. Even nostrils, eyebrows, everything!
gpt
Hair is made of the same stuff as your skin, but it contains more of something called keratin, which makes the hair so strong. Your nails have it, too. 

Hair has a few purposes. For one, you can feel a gentle touch before your skin is touched. 

It acts as a filter for dust, dirt, and other tiny things -- this is especially important with your eyelashes and eyebrows... Also inside your nose!  

When you are older, you grow pubic hair, which is very thick hair that grows around your genitals. It also acts as a filter for dust, bacteria, and dirt, but also acts as a lubricant to help prevent your skin becoming sore or raw while walking or moving. It also lets others know that you are more grown up than younger people. 

The most primal/basic purpose of hair is to protect you against the cold. When we are cold, we get goose bumps -- this is from itty bitty little tiny muscles inside your skin that hold your hair upright. Way back when we were much more hairy, this would make our hair stand up like a hat or a sweater and would trap heat inside of it, keeping us warmer. 

For some people, their hair are thicker on their head to protect against the heat of the sun (sometimes called "nappy" hair).