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The prompt phase of gamma-ray bursts (GRBs) is the brightest electromagnetic phenomenon in the Universe, likely powered by a relativistic jet from a black hole central engine. Internal shocks, arising from collisions between faster and slower material within the jet, are leading candidates for the energy dissipation process. Each collision produces a reverse shock into the faster material and a forward shock into the slower one. In this talk, I will discuss the dynamics of such shocks and show that their internal energy dissipation efficiencies and shock crossing timescales differ significantly under general conditions. I will explain how this asymmetry helps account for key features of GRB prompt emission, such as energy-dependent pulse shapes, the hard-to-soft evolution of the peak photon energy, and the double-humped spectral structure. I will also propose that the low-energy spectral break in the hard X-ray band may result from a weak forward shock rather than a thermal component, and show how this framework explains the off-axis suppression of gamma-ray emission in structured jets.