Type Ia supernovae are critical tools for measuring the expansion rate of the universe and its geometry. These explosions are believed to result from the thermonuclear disruption of white dwarfs approaching the Chandrasekhar mass (≈1.39 M☉), either as carbon-oxygen white dwarfs or sub-Chandrasekhar models with a helium shell. Despite this, the exact mechanism of explosion remains uncertain. Recent models and observations have provided insights into the diversity of Type Ia supernovae, showing variations in light curves, spectra, and progenitor properties. Observational data indicate that Type Ia supernovae are homogeneous in their spectral and photometric properties, with a strong correlation between light curve width and peak brightness. This has led to the use of Type Ia supernovae as standardizable candles for cosmological studies. However, the observed diversity suggests that not all Type Ia supernovae may originate from the same progenitor system or explosion mechanism. Theoretical models of Type Ia supernovae involve complex processes such as thermonuclear combustion in degenerate stars, radiative transfer, and the role of radioactive nickel in powering light curves. Numerical simulations have been used to study these processes, but challenges remain in accurately modeling the explosion physics and opacities. Observational constraints, such as the absence of hydrogen lines and the presence of silicon features, support the idea of carbon-oxygen white dwarf explosions. However, the diversity in observed properties suggests that different progenitor systems or explosion mechanisms may be responsible for different sub-classes of Type Ia supernovae. Progenitor systems for Type Ia supernovae are likely binary systems, with either a single-degenerate scenario (a white dwarf accreting from a companion star) or a double-degenerate scenario (two white dwarfs merging). While both scenarios have been proposed, the single-degenerate model is currently more favored due to the difficulty in explaining the observed homogeneity of Type Ia supernovae with the double-degenerate model. The accretion of hydrogen onto white dwarfs can lead to various outcomes, including novae, sub-Chandrasekhar explosions, or the eventual explosion of a white dwarf at or near the Chandrasekhar mass. Observational evidence, such as the existence of supersoft X-ray sources, supports the possibility of white dwarfs accreting sufficient mass to reach the Chandrasekhar mass and explode as Type Ia supernovae.Type Ia supernovae are critical tools for measuring the expansion rate of the universe and its geometry. These explosions are believed to result from the thermonuclear disruption of white dwarfs approaching the Chandrasekhar mass (≈1.39 M☉), either as carbon-oxygen white dwarfs or sub-Chandrasekhar models with a helium shell. Despite this, the exact mechanism of explosion remains uncertain. Recent models and observations have provided insights into the diversity of Type Ia supernovae, showing variations in light curves, spectra, and progenitor properties. Observational data indicate that Type Ia supernovae are homogeneous in their spectral and photometric properties, with a strong correlation between light curve width and peak brightness. This has led to the use of Type Ia supernovae as standardizable candles for cosmological studies. However, the observed diversity suggests that not all Type Ia supernovae may originate from the same progenitor system or explosion mechanism. Theoretical models of Type Ia supernovae involve complex processes such as thermonuclear combustion in degenerate stars, radiative transfer, and the role of radioactive nickel in powering light curves. Numerical simulations have been used to study these processes, but challenges remain in accurately modeling the explosion physics and opacities. Observational constraints, such as the absence of hydrogen lines and the presence of silicon features, support the idea of carbon-oxygen white dwarf explosions. However, the diversity in observed properties suggests that different progenitor systems or explosion mechanisms may be responsible for different sub-classes of Type Ia supernovae. Progenitor systems for Type Ia supernovae are likely binary systems, with either a single-degenerate scenario (a white dwarf accreting from a companion star) or a double-degenerate scenario (two white dwarfs merging). While both scenarios have been proposed, the single-degenerate model is currently more favored due to the difficulty in explaining the observed homogeneity of Type Ia supernovae with the double-degenerate model. The accretion of hydrogen onto white dwarfs can lead to various outcomes, including novae, sub-Chandrasekhar explosions, or the eventual explosion of a white dwarf at or near the Chandrasekhar mass. Observational evidence, such as the existence of supersoft X-ray sources, supports the possibility of white dwarfs accreting sufficient mass to reach the Chandrasekhar mass and explode as Type Ia supernovae.