A zero degree angle appears as a straight line that travels from the point of inception to the right or positive side of a number line. If the line travels both left and right from the point of inception, it is considered a 180 degree angle or straight angle.
Angles are measured in degrees ranging from zero to 360. A 360 degree angle starts at the point of inception and travels in a complete circle to once again reach the point of inception. This is why there are 360 degrees in one rotation. In math, the term "degree" is represented by a small circle appearing at the upper right corner of the number in question.