A tracking array is a solar array that follows the path of the sun to maximize the solar radiation incident on the photovoltaic surface. The two most common orientations are:
Tracking arrays use both direct and diffuse sunlight. Two-axis tracking arrays capture the maximum possible daily energy. Typically, a single-axis tracker will give 15% to 25% more power per day than a fixed array, and dual-axis tracking will add about 5% to that. The exact gains will depend somewhat on latitude and season.
For more information, see solar tracker.