These lecture notes summarize the theory of equations of associativity describing the geometry of moduli spaces of 2D topological field theories. The main focus is on the Witten-Dijkgraaf-Vafa-Verlinde (WDVV) equations, which describe the associativity of a Frobenius manifold. A Frobenius manifold is a manifold equipped with a flat metric, a covariantly constant unity vector field, and a symmetric 3-tensor that satisfies certain associativity conditions. The WDVV equations are a system of nonlinear partial differential equations that arise from the requirement that the third derivatives of a function F(t) satisfy the associativity condition. The solutions of the WDVV equations describe the moduli space of topological conformal field theories. The lectures also discuss the geometric reformulation of the WDVV equations, the role of the Euler vector field, and the connection between the WDVV equations and integrable hierarchies. The lectures also cover the properties of Frobenius manifolds, including their symmetries, the monodromy group, and the relation to the theory of Painlevé equations. The lectures conclude with a discussion of the applications of Frobenius manifolds in physics, particularly in the context of topological field theories and mirror symmetry.These lecture notes summarize the theory of equations of associativity describing the geometry of moduli spaces of 2D topological field theories. The main focus is on the Witten-Dijkgraaf-Vafa-Verlinde (WDVV) equations, which describe the associativity of a Frobenius manifold. A Frobenius manifold is a manifold equipped with a flat metric, a covariantly constant unity vector field, and a symmetric 3-tensor that satisfies certain associativity conditions. The WDVV equations are a system of nonlinear partial differential equations that arise from the requirement that the third derivatives of a function F(t) satisfy the associativity condition. The solutions of the WDVV equations describe the moduli space of topological conformal field theories. The lectures also discuss the geometric reformulation of the WDVV equations, the role of the Euler vector field, and the connection between the WDVV equations and integrable hierarchies. The lectures also cover the properties of Frobenius manifolds, including their symmetries, the monodromy group, and the relation to the theory of Painlevé equations. The lectures conclude with a discussion of the applications of Frobenius manifolds in physics, particularly in the context of topological field theories and mirror symmetry.