The Gaia mission has significantly advanced the study of binary stars, providing high-precision astrometry for over a billion stars in the Milky Way. Binary stars are crucial for understanding stellar mass, radius, and evolutionary models, as well as for explaining phenomena like supernovae and gamma-ray bursts. Gaia's data has enabled a more accurate census of binary populations and the discovery of rare objects, particularly wide binaries (separations > 100 au). It has also revealed evidence of binarity through astrometric noise and proper motion anomalies, and has provided astrometric and radial velocity orbits from Gaia DR3. Binaries containing non-accreting compact objects have also been studied. However, Gaia's data has limitations, and ground-based follow-up is essential. Future improvements with Gaia DR4 are expected to enhance these studies. Gaia's angular resolution of ~1 arcsec allows it to resolve wide binaries, with separations of ~1000 au at 1 kpc. The mission's 0.1 arcsec diffraction limit will eventually resolve closer pairs. Gaia's sensitivity varies with separation, with higher sensitivity at closer distances. The mission has enabled the study of wide binary populations, revealing a bimodal separation distribution, and has identified wide white dwarf binaries, which provide insights into the age of companions. The separation distribution of wide binaries is sensitive to metallicity, with a stronger anticorrelation at closer separations. Gaia has also helped identify hierarchical triples and quadruples, with speckle imaging revealing inner binaries that are unresolved by Gaia. Gaia's data has been used to study the eccentricity distribution of wide binaries, revealing a super-thermal distribution at wide separations. The mass ratio distribution of wide binaries shows a preference for higher mass ratios than expected, with a population of equal-mass "twin" binaries. The presence of planets in wide binary systems suggests correlated formation processes. Gaia has also been used to test modified gravity theories, with studies showing that the gravitational force law inferred from wide binary data is still debated. Gaia's astrometric data has been used to constrain the mass-luminosity relation, and to measure the masses of stars with wide companions. The mission's data has also been used to study the effects of higher-order multiplicity on the observed velocity differences of wide binaries. Despite these advances, challenges remain in distinguishing true binaries from chance alignments and in accurately modeling the population of unresolved inner binaries. Future studies with improved data and follow-up observations will further refine our understanding of binary star systems.The Gaia mission has significantly advanced the study of binary stars, providing high-precision astrometry for over a billion stars in the Milky Way. Binary stars are crucial for understanding stellar mass, radius, and evolutionary models, as well as for explaining phenomena like supernovae and gamma-ray bursts. Gaia's data has enabled a more accurate census of binary populations and the discovery of rare objects, particularly wide binaries (separations > 100 au). It has also revealed evidence of binarity through astrometric noise and proper motion anomalies, and has provided astrometric and radial velocity orbits from Gaia DR3. Binaries containing non-accreting compact objects have also been studied. However, Gaia's data has limitations, and ground-based follow-up is essential. Future improvements with Gaia DR4 are expected to enhance these studies. Gaia's angular resolution of ~1 arcsec allows it to resolve wide binaries, with separations of ~1000 au at 1 kpc. The mission's 0.1 arcsec diffraction limit will eventually resolve closer pairs. Gaia's sensitivity varies with separation, with higher sensitivity at closer distances. The mission has enabled the study of wide binary populations, revealing a bimodal separation distribution, and has identified wide white dwarf binaries, which provide insights into the age of companions. The separation distribution of wide binaries is sensitive to metallicity, with a stronger anticorrelation at closer separations. Gaia has also helped identify hierarchical triples and quadruples, with speckle imaging revealing inner binaries that are unresolved by Gaia. Gaia's data has been used to study the eccentricity distribution of wide binaries, revealing a super-thermal distribution at wide separations. The mass ratio distribution of wide binaries shows a preference for higher mass ratios than expected, with a population of equal-mass "twin" binaries. The presence of planets in wide binary systems suggests correlated formation processes. Gaia has also been used to test modified gravity theories, with studies showing that the gravitational force law inferred from wide binary data is still debated. Gaia's astrometric data has been used to constrain the mass-luminosity relation, and to measure the masses of stars with wide companions. The mission's data has also been used to study the effects of higher-order multiplicity on the observed velocity differences of wide binaries. Despite these advances, challenges remain in distinguishing true binaries from chance alignments and in accurately modeling the population of unresolved inner binaries. Future studies with improved data and follow-up observations will further refine our understanding of binary star systems.