What is the difference between interface and type?

Both describe object shapes, but differ in capabilities:

Interface

• Supports declaration merging.
• Better for public API contracts and extending object shapes.

Type

• Supports unions, intersections, tuples, and mapped/conditional types.
• Cannot be reopened/merged after creation.

For simple object shapes either works. Prefer interface for extendable object contracts; prefer type for unions and advanced type logic.