AJAX

(Asynchronous JavaScript and XML) A way of including content in a web page in which javascript code in the web page fetches some data from a server and displays it without re-fetching the entire surrounding page at the same time (hence the 'Asynchronous')

Often (but not always) the data fetched by the javascript code is in XML format.

It is common for Ajax applications to update the Ajax content multiple times without the surrounding page needing to be updated even once.

A simple example of Ajax would be a weather-forcast box in the middle of a web page. Ajax could be used to populate the box every 5 minutes without needing to refresh the surrounding page.

Applet

A small Java program that can be embedded in an HTML page. Applets differ from full-fledged Java applications in that they are not allowed to access certain resources on the local computer, such as files and serial devices (modems, printers, etc.), and are prohibited from communicating with most other computers across a network. The common rule is that an applet can only make an Internet connection to the computer from which the applet was sent.

ASP

(Application Service Provider) A organization (usually a business) that runs one or more applications on their own servers and provides (usually for a fee) access to others. Common examples of services provided this way include web-based software such as Calendar systems, Human Resources tools (timesheets, benefits, etc.), and various applications to help groups collaborate on projects.