Gamma-ray bursts are one of the most energetic events in the universe. A fast variability and observed spectrum demand that the emitting region of the GRBs has to move relativistically in order to escape annihilation of the photons in a photon dense environment. Speeds can even attain superluminal values and a transition of GRB jets from subluminal to superluminal speed can explain some of the features observed in the lightcurves. Several methods have been proposed to measure the Lorentz factor such as the deceleration of the blast wave, compactness problem, exploiting the thermal emission component, and others, but, these lead to different and at times conflicting estimates. The underlying physics both of the inner engine and of the emission process acting in the GRBs is still elusive, and the Lorentz factor is crucial to understand it. A review of the methods to measure the Lorentz factor of the GRBs will be presented with a case study of GRB 190114C which is also the first GRB to show teraelectronvolt emission. I will also highlight the recent developments in the understanding of GRBs in the multi-messenger era and some of the challenges posed by the proposed solutions.