A prominence is a bright arched cloud of ionized gas in the chromosphere and corona of the Sun. It is mostly contained in the sun's magnetic field. A solar flare, however, is a ejection of mass from the sun that actually comes in contact with the rest of the solar system.
I think this will help you "Think of solar prominence as the Sun stretching out its gas components to a length that can reach thousands of kilometers... solar flares are similar to this only that it snaps at the peak of its stretch... solar prominences are usually harmless... nobody would want a solar flare to happen as this will entail a damaging surge of energy... coronal mass ejections [are] more powerful and therefore more harmful to Earth life..."
Hope I helped you