This talk will summarize the observations of G2 and current models about its nature. The existence of such a tiny, cold gas cloud in the hostile vicinity of the SMBH raises numerous fascinating questions. Is G2 a diffuse gas clump that originates from winds of high-mass stars in the surrounding stellar disk or is it the atmosphere of an evaporating, invisible protostellar disk, planet or star? Or is it something completely different? Where did it come from and where will it go? Why is it on such a highly eccentric orbit? Which physical processes constrain its properties like its size, mass, density, temperature and geometrical shape? How many clouds like G2 are currently orbiting Sgr A* and how do they affect its activity and gas accretion rate? Like comet Shoemaker Levy's 1994 collision with Jupiter, the big challenge has started for astrophysicists to predict the outcome of G2's close encounter with the SMBH in the year 2013 and beyond. Their models will be validated directly by observations within the next couple of years.