Explain the differences between HTTP POST and PUT requests in the context of web development.

Main differences between HTTP requests POST and PUT:

• POST is used to create a new resource. It sends data to the server, and the server usually creates a new object with a unique identifier.
• PUT is used to update an existing resource or create a resource at a specified URI. The PUT request is idempotent — repeated calls with the same data will not change the result.

Example:

• POST /users — creates a new user, the server assigns an ID.
• PUT /users/123 — updates the user with ID 123 or creates it if it does not exist.

Thus, POST is for adding, PUT is for replacing or updating.