namespace is the folder where your images are stored on the media manager.
There are a number of options you can use with the gallery function.
120×120 limits the size of images to 120×120. - The
showtitle means that you can make a caption by writing it into the
title section of the image metadata on the image manager. This only works with jpegs. - The
450×450 sets the size of images within the lightbox to 450×450.