They look like eruptions, but time-lapse pictures show material moving downward even more often than upward. Their material is actually cooler than the surrounding corona. Their shapes seem to follow the magnetic field lines of the sun's magnetic field, in huge loops, arches, and streamers. The typical prominence is a quiescent prominence , which remains in place for a good fraction of a day. Flares are very violent and rapid explosions on the sun.
Smaller ones last a few minutes, major ones several hours.
Recent solar space observatories have been able to make motion pictures of these CME's. The general term we should use for the phenomenon is an active region , a place on the sun where sunspots, flares, and plages occur.