Scientists track sunspots that are part of active regions, which often produce large explosions on the sun such as solar flares and coronal mass ejections (CMEs). Each time an active region appears it is assigned a number.
Active regions that have survived their trip around the back of the sun and reappear are assigned a new number - a convention left over from when we had no telescopes observing the far side of the sun and so could not be sure that the new sunspot was indeed the same as the old one.
This active region is currently labeled AR11990. Last time around it was labeled AR11967 and its first time it was AR11944.
During its three trips thus far, this region has produced two significant solar flares, labeled as the strongest kind of flare, an X-class.