Poisson algebras have become an essential topic in mathematics with a rich structure and wide applicability. Despite numerous resources available on Poisson structures, the algebraic side of the story remains relatively less explored. This paper presents an extended version of a mini-course given during the virtual Winter School and Workshop "Wisla 20-21." The course covers various aspects of Poisson algebras, focusing on both algebraic and geometric perspectives. While most of the lectures cover established results, the final chapter includes recent classification results on "low rank" double quadratic Poisson brackets.