The gravitational-wave event GW170817 was detected by the Advanced LIGO and Advanced Virgo detectors on August 17, 2017, marking the first observation of a binary neutron star (BNS) inspiral. The signal, with a combined signal-to-noise ratio of 32.4, was localized to a sky region of 28 deg² and had a luminosity distance of 40±8 Mpc, the closest and most precisely localized gravitational-wave signal. The event was associated with the gamma-ray burst GRB 170817A, confirming the hypothesis of a neutron star merger and providing the first direct evidence of a link between BNS mergers and short gamma-ray bursts. Electromagnetic follow-up observations confirmed the event as a neutron star merger. The component masses of the binary were inferred to be between 0.86 and 2.26 solar masses, with the total mass of the system being 2.74±0.04 solar masses. The source was localized to a region near the galaxy NGC 4993, and the event provided insights into astrophysics, dense matter, gravity, and cosmology. The detection of GW170817 confirmed the long-standing hypothesis that BNS mergers are linked to short gamma-ray bursts. The event also provided a direct measurement of the luminosity distance of the source, which, combined with a redshift measurement, can be used to infer cosmological parameters independently of the cosmic distance ladder. The Hubble constant was inferred to be 70±12 km s⁻¹ Mpc⁻¹, consistent with the value from Planck. The event marked the beginning of a new era of discovery in gravitational-wave astronomy, offering unprecedented joint gravitational and electromagnetic observations.The gravitational-wave event GW170817 was detected by the Advanced LIGO and Advanced Virgo detectors on August 17, 2017, marking the first observation of a binary neutron star (BNS) inspiral. The signal, with a combined signal-to-noise ratio of 32.4, was localized to a sky region of 28 deg² and had a luminosity distance of 40±8 Mpc, the closest and most precisely localized gravitational-wave signal. The event was associated with the gamma-ray burst GRB 170817A, confirming the hypothesis of a neutron star merger and providing the first direct evidence of a link between BNS mergers and short gamma-ray bursts. Electromagnetic follow-up observations confirmed the event as a neutron star merger. The component masses of the binary were inferred to be between 0.86 and 2.26 solar masses, with the total mass of the system being 2.74±0.04 solar masses. The source was localized to a region near the galaxy NGC 4993, and the event provided insights into astrophysics, dense matter, gravity, and cosmology. The detection of GW170817 confirmed the long-standing hypothesis that BNS mergers are linked to short gamma-ray bursts. The event also provided a direct measurement of the luminosity distance of the source, which, combined with a redshift measurement, can be used to infer cosmological parameters independently of the cosmic distance ladder. The Hubble constant was inferred to be 70±12 km s⁻¹ Mpc⁻¹, consistent with the value from Planck. The event marked the beginning of a new era of discovery in gravitational-wave astronomy, offering unprecedented joint gravitational and electromagnetic observations.