GRB fireball physics:: prompt and early emission

We review the fireball shock model of gamma-ray burst (GRB) prompt and early afterglow emission in the light of rapid follow-up measurements made and enabled by the multi-wavelength Swift satellite. These observations are leading to a reappraisal and expansion of the previous standard view of the GRB and its fireball. New information on the behaviour of the burst and afterglow on minutes to hour timescales has led, among other results, to the discovery and follow-up of short GRB afterglows, the opening up of the z greater than or similar to 6 redshift range, and the first prompt multi-wavelength observations of a long GRB-supernova. We discuss the salient observational results and some associated theoretical issues.