AJAX and HTTP

HTTP

HTTP defines a set of request methods to indicate the desired action to be performed for a given resource. Although they can also be nouns, these request methods are sometimes referred as HTTP verbs. Each of them implements a different semantic, but some common features are shared by a group of them: e.g. a request method can be safe, idempotent, or cacheable.

AJAX

GET
    The GET method requests a representation of the specified resource. Requests using GET should only retrieve data.

Example:
xhttp.open("GET", "ajax_info.txt", true);
xhttp.send();

HEAD
    The HEAD method asks for a response identical to that of a GET request, but without the response body.

POST
    The POST method is used to submit an entity to the specified resource, often causing a change in state or side effects on the server.

Example:
xhttp.open("POST", "demo_post2.asp", true);
xhttp.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
xhttp.send("fname=Henry&lname=Ford");

PUT
    The PUT method replaces all current representations of the target resource with the request payload.

DELETE
    The DELETE method deletes the specified resource.