Solar Flares are nothing more than giagantic explosions of energy on the Sun. They emit radiation from all different wavelengths of of the electro-magnetic spectrum. Flares can explode with as much energy as hundreds of thousands and in some cases millions of nuclear bombs. In the pciture above you see a prominence comint out of the sun with the Earth drawn to scale just to show how large some of the things that occur on the surface of the Sun are.
Looking at the size of this prominence with respect to the Earth is it any wonder that some events occuring on the Sun can have large scale effects here on the Earth? How large, and what effects these and other solar events have on our terrestrial environment here on Earth some 93,000,000 miles away is still the area of much research by scientists today. If a method of predicting what is going to happen on the Sun can be done very accurately and we know what effects these solar events will have on the Earth we can prepare for them much more effectively. The name of the game in doing these predictions though is two-fold you must have both accuracy and time. For the longer scale Solar events some lasting years to decades the effects on Earth could be devastating, however with lead time some preparations could be made to eliminate or limit some of the effects.
If you wish to learn more about Solar Flares NASA runs a website that is very very informative on the subject. Just click HERE to be taken to that site.