Boxers are meant to be worn in the waistband, which is a bit lower than the belly button. They can also be worn in the waistband, which is slightly higher than the belly button, or without the waistband at all.
Boxers are meant to be worn under shorts and pants. They can also be worn alone if you want to.
They are made of cotton, which is a natural fiber that’s soft and comfortable. The boxer-brief style is longer than the boxer-trunks style, so it gives you room to move around without being constricted.