- Mainly to sense things. But don't pull them. you will throw their balance off!
- In general whiskers help them sense things in their surroundings. Whiskers on dogs and cats also measure how wide a narrow tunnel / burrow or hole is, and can improve their spacial awareness by acting not unlike a record player stylus detecting small vibrations and air movements around them.
The term Billy Tea refers to tea brewed in a billy can, that is a small can, tin or pot used on a campfire for boiling water/tea etc. A common brand of tea sold in Oz is also called Billy Tea. So the term "billy up to the fire" basically means, "put the kettle on".