What is the difference between type and interface in TypeScript?

Key differences: 1) Declaration merging - interfaces can be merged, types cannot, 2) Extensibility - interfaces use extends, types use intersection (&), 3) Computed properties - types support computed properties, interfaces do not, 4) Union types - types can represent unions, interfaces cannot directly, 5) Primitive types - types can alias primitives, interfaces cannot, 6) Performance - interfaces are generally faster for object types. Use interfaces for object shapes that might be extended, types for unions and computed properties.