Ten degrees is the width of your fist at arm's length. This is a rare event that occurs when Earth encounters closely grouped meteors within a meteor stream. Such events can see meteor rates exceeding 1000 per minute. When the comet comes close to the Sun, the dust and gas is pushed away from the comet's head. This extension from the coma is called the tail.
Tails typically point away from the Sun, and can be straight, curved, or fan-shaped.
A comet can have more than one tail.