The Fermi Large Area Telescope (LAT) observations of the active Sun provide the largest sample of detected solar flares with emission greater than 30 MeV to date. These include detections of impulsive and sustained emission, extending up to ~20 hours in the case of the 2012 March 7 X-class flares. Of particular interest is the first detection of >100 MeV gamma-ray emission from three solar flares whose positions behind the limb were confirmed by the STEREO spacecrafts. The LAT data provides a new observational channel that, when combined with observations from across the electromagnetic spectrum, provide a unique opportunity to diagnose the mechanisms of high-energy emission and particle acceleration in solar flares. We will present an overview of these observations including the emission of the Sun in its quiescent state and discuss how these observations provide constrains on different emission mechanisms.