Abstract algebra is the study of algebraic structures like groups, rings, and fields. It emerged in the early 20th century to make algebra more rigorous and abstract. Key developments included the study of symmetry in polynomial equations, which led to the concepts of groups, and the algebraic investigation of quadratic and higher-degree equations, which produced the ideas of rings and ideals. Now abstract algebra is used throughout mathematics and in fields like physics, where group theory can simplify differential equations and describe system symmetries.