Using [Web Method]

Hi there
              Can anyone explain about this [WebMethod] call using Javascript. I have created application for ordinary insert ,select, Delete using this [webMethod] and javascript call. Seems its faster and its useful a lot for my application.
Small Example below

.aspx
<script>

function test() {
                var text1 = document.getElementById("<%= TextBox1.ClientID %>").value;
                var text2 = document.getElementById("<%= TextBox2.ClientID %>").value;
                PageMethods.Testing(text1,text2, success);

          & ...