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Gamma-ray bursts (GRBs) are flashes of gamma-rays occurring at cosmological distances (for a recent review see [1]).They are divided into two classesbased on their prompt emission durations: short-duration (＜ 2 seconds) hard-spectrum bursts and long-duration soft-spectrum bursts (＞ 2 seconds).The observations (including discoveries of both the gravitational wave event GW170817 from an inspiral of two neutron stars and its electromagnetic counterparts) indicate that long-duration GRBs result from core collapses of massive stars and short-duration GRBs are produced from mergers of neutron star-neutron star binaries or black hole-neutron star binaries.After the prompt phase, multi-wavelength (X-ray, optical and radio) afterglows of GRBs have been detected, and in particular, during an early afterglow phase, X-ray flares from a great number of GRB sources have been observed.Two important questions appear:What's the prompt phase physical mechanism of GRBs?Do X-ray flares have a similar origin?