Explain the differences between HTTP POST, PUT, and PATCH methods in web development.

HTTP methods POST, PUT, and PATCH are used to send data to the server but have different semantics:

• POST — creates a new resource. Usually used for adding new data. POST requests are not idempotent (repeating the request may create multiple resources).

• PUT — completely replaces an existing resource or creates it if it does not exist. PUT requests are idempotent (repeating the same request with the same data will not change the result).

• PATCH — partially updates an existing resource, changing only specified fields. Also idempotent, but used for partial modifications.

Example:

• POST /users — create a new user
• PUT /users/123 — replace data of the user with ID 123
• PATCH /users/123 — update specific fields of the user with ID 123