An HTTP GET request is what you get (pardon the pun) when you enter a URI in your browser or when you click on a link on a web page. Certain HTML elements, like
<img> also generate GET requests. GET requests a resource (usually a web page or an image) from the server. You can pass additional information to a server-side script by adding 'query parameters' after the script, such as http://example.com?foo&bar=42.
A POST request is similar to a GET request. The difference is that any additional information is sent in the body of the request, rather than as part of the URI. You can generate POST requests using
<form method="post"> elements in HTML, where the form field values are sent in the request body.
A HEAD request is also similar to a GET request, but the server responds only with the HTTP headers; the response body is empty.
A PUT request is a way to upload a file to a server. Most servers don't allow PUT requests, because of the security implications.
Similarly, a DELETE request will delete a resource on the server. Like PUT, this method is rarely permitted on server for obvious reasons.