What is the difference between struct and class in Swift?

Key differences: 1) Value vs Reference types - structs are value types (copied), classes are reference types (shared), 2) Inheritance - classes support inheritance, structs do not, 3) Identity operators - classes use === and !==, structs cannot, 4) Deinitializers - only classes have deinit, 5) Reference counting - only classes use ARC, 6) Mutability - struct methods need mutating keyword to modify properties. Use structs for simple data, classes for complex objects with inheritance.