What HTTP methods are there and what are they used for?

Main HTTP methods and their purpose:

• GET — retrieve a resource. Safe and idempotent method, does not change server state.
• POST — create a new resource or perform an action. Can change state, not idempotent.
• PUT — replace the entire resource. Idempotent.
• PATCH — partially update a resource. Not always idempotent.
• DELETE — delete a resource. Idempotent.
• HEAD — get only the headers of a resource, without the body.
• OPTIONS — find out supported methods and server capabilities for a resource.

Example: for REST API

• GET /users/123 — get user with id 123
• POST /users — create a new user
• PUT /users/123 — replace data of user 123
• PATCH /users/123 — update part of user 123's data
• DELETE /users/123 — delete user 123

Understanding these methods is important for proper design and use of web services.