Multiwavelength Observations, Spectral Energy Distributions, and Variability of Blazars

This literature review examines blazars as an extreme subclass of active galactic nuclei, focusing on their multiwavelength observational properties, spectral energy distributions, variability, and high-energy emission mechanisms. It discusses observations across the electromagnetic spectrum, including radio, infrared, optical, ultraviolet, X-ray, and gamma-ray bands. Particular attention is given to synchrotron radiation, inverse Compton scattering, Synchrotron Self-Compton and External Compton models, as well as hadronic emission scenarios. The review also discusses variability, multi-messenger connections, current challenges, and future observational prospects in blazar research.