Taken from wikipedia
In photography, the golden hour (also known as magic hour) is the first and last hour of sunlight during the day when a specific photographic effect is achieved with the quality of the light during these hours.
Typically, lighting will be softer (more diffuse) and warm in hue, and shadows will be quite pronounced as a result of the sun being so close to the horizon. The sunlight is traveling obliquely (through more of the atmosphere) and striking objects at an angle, instead of straight down. The golden hour is a mild version of alpenglow, as described by Galen Rowell.