A-level Computing/AQA/Problem Solving, Programming, Operating Systems, Databases and Networking/Communication and Networking/Server-side scripting
Common Gateway Interface (CGI) 
<form></form> <input> <select> <option> </option> <option> </option> <option> </option> </select> <textarea></textarea>
There are some new ones added to html5
Server-side scripting – the basis of dynamic web page content.
You can learn more about how AJAX works over at w3schools.