HETE-2 (High Energy Transient Explorer) is a small scientific satellite whose main task is to detect Gamma-Ray Bursts, promptly determine their coordinates, when possible, and distribute them immediately to the scientific community. HETE-2 has detected many of the most interesting events in recent years: GRB030329, which confirmed beyond any doubt the Gamma-Ray Burst - Supernova connection; GRB021211, also connected to a SN, in this case at high redshift; and other well observed and studied bursts, for example GRB021004 and GRB030226. The prompt localization by HETE-2 of a "short" GRB allowed the first detection of an X-ray afterglow for this class of events. The energy range of the HETE-2 detectors, which starts at a few keVs, has allowed extension of the study of spectral and global properties of "classical" GRBs to the softer X Ray Flashes and X-Ray Rich events and the first redshift determination for a X-Ray Flash. HETE-2 has detected also hundreds of X-ray bursts and events from Soft Gamma-ray Repeaters; in some cases it was the first experiment to find that one of those sources had entered a new active phase.