Dyanmic transition gallery

Hello, I understand the way how to load an external “.jpg/.swf” but I do not know how these guy do this little transition. For example, I click on an image, it fades in, that I know how to do, you can animate the image in an external .swf file but the thing i dont get is how they get the fadeout? like instead of it abrubtly dissapearing it fadesout and makes way for the next pic or selection. here is what i am talking about:

http://www.templatehelp.com/aff/preview.php?aff=flash_templates&skin=22&locale=en&currency=0&pr=yes&src=yes&nt=yes&help=yes&sample=yes&faq=yes&nmg=yes&auth=yes&down=yes&chm=&hide_flash=0&search=&PHPSESSID=b6b2106f860bccd81a81c78470a4bbcb&referer=http%3A%2F%2Fwww.bestflashanimationsite.com%2Ftemplates%2Fflash-site%2F&i=15716

I really want to know how they did it, they also use this flawless transition on Acura’s site for example i pick car#1, it fades in to fade car#1, when i pick the next car (car#2) it fadesout car#1 and fades in car#2 and so, etc. I would really like to know how to accomplish that. :-/ =)