On July 28, 2012, our sun emitted a mid-level flare which was subsequently categorized as an M6.2 by NASA scientists.
As you can see, the flare is visible in this image (lower left-hand side). It apparently originated from an active region on the sun known as sector AR 1532.
The picture was snapped by NASA's Solar Dynamics Observatory (SDO) in the 131 Angstrom wavelength, which is typically colorized in teal and is a particularly good wavelength for observing flares.
According to astronomers, solar flares can best be described as powerful bursts of radiation. Fortunately, harmful radiation from a flare cannot pass through Earth's atmosphere to affect humans on the ground.
However, when sufficiently intense they are capable of disturbing the atmosphere in the layer where GPS and communications signals travel. This disrupts the radio signals for as long as the flare is ongoing, which can last anywhere from minutes to hours.
As noted above, the July 28th flare was classified as an M6.2. Although M-class flares are considered the weakest flares, they can still cause some space weather effects near Earth, such as brief radio blackouts at the poles.
Increased numbers of flares are quite common at the moment, since the sun's normal 11-year activity cycle is ramping up toward solar maximum in 2013.