Lagrangian Floer theory, from geometry to algebra and back again

We survey various aspects of Floer theory and its place in modern symplectic geometry, from its introduction to address classical conjectures of Arnold about Hamiltonian diffeomorphisms and Lagrangian submanifolds, to the rich algebraic structures captured by the Fukaya category, and finally to the idea, motivated by mirror symmetry, of a “geometry of Floer theory” centered around family Floer cohomology and local-to-global principles for Fukaya categories.