Optical and near-infrared flares in GRB afterglows

Among the diversities in the very early evolution of GRB afterglows are bright optical/near-infrared flares before or superimposed onto an otherwise smoothly decaying afterglow light curve. A lot has been learned about GRBs by using an optical flare or lack thereof as a diagnostic of the emission mechanisms and outflow conditions. In this contribution I will review the observational properties of rising and decaying light-curves in GRB afterglows, discuss their possible physical origins, and highlight in which way they help in understanding GRB and afterglows physics.