The POST method is an HTTP request used to send data to a server for processing. Unlike the GET method, which appends data to the URL, the POST method includes the data in the body of the request. This allows for larger amounts of data to be sent securely, making it ideal for submitting forms or uploading files. When a client, such as a web browser, uses the POST method, the server processes the received data and typically returns a response. This response can include confirmation of the action taken, such as creating a new resource or updating existing information in a database, often represented in formats like JSON or XML.