They're perfect for when you need to floss on the go and normal flossing would be overly conspicuous or just gross (excuse me while I unspool this long thread in this gas station bathroom).

Dental floss is a thin, soft thread made of nylon or plastic which removes food and plaque from between your teeth. If you use dental floss incorrectly, it can damage your gums.

The same applies when you floss. Generally, we are taught to brush our teeth and then use floss to remove anything the toothbrush missed. Even at the dentist's office, they follow the same steps.