AJAX stands for Asynchronous JavaScript and XML. It's a way of making a
web client (i.e. browser) seem like a rich client (windows app) by using
background HTTP requests to the server, and numerous client scripts. You
get very fancy functionality at the expense of the loading time required
for the page (since now the browser has to download the HTML and any/all
javascript files).
ATLAS is now called "ASP.NET AJAX", and is Microsoft's implementation of
AJAX within the ASP.NET world. It fits "fairly well" into ASP.NET pages.
Web Parts is a Microsoft term for a partial "Web Control" (partial web
page) that is made to embed in another page. It's perfect for
aggregating content from numerous sources on one page, and allows the
user to rearrange the Web Parts dynamically (similar to iGoogle). It has
nothing to do with AJAX, but is almost as cool.
Steve C.
MCAD,MCSE,MCP+I,CNE,CNA,CCNA