Photo slideshow gallery

Hi,
I purchased a readymade slideshow for my photography website. I would like to create something similar myself so I can resize and reposition the images. I particularly like the effect of the small thumbnail becoming the large image but I don’t know what this effect is called to start Googling for a tutorial.
Could some kind person please take a look and let me know what I should be searching for.
http://www.lisajanescott.net
Thank you.