The user needs to browse a series multiple images in a high resolution.
A gallery consists of multiple images that can be browsed one by one by navigating between them. Only one image is viewed at a time. Often, several different options for navigating the gallery is provided in order to accomodate several different browsing behaviors of the different kinds of users browsing the gallery. Similar to almost all galleries is stating the context the current image image being views as in “Image 2 out of 18 images”, the shorter “2 out of 18”, or merely “2/18”.
Thumbnails allow the user to find out where he or she is in the gallery: the context of the current image. Thumbnails also provide a great way to keep the user in the flow of going to the next image; if the image seems interesting in thumbnail mode it might be worth a click from the user’s perspective.
Listing the gallery images as numbers allow for quick navigation. Highlight the current image to let the user know where he or she is in the gallery: the context of the current image.
Galleries (or slideshows) work in one of two ways: either they switch automatically from image to image after a set time interval, or buttons and other navigation elements are provided to let the user browse through images manually. Some galleries provide pause buttons and thus provides a mix between the two.
1 Slideshows In Web Design: When And How To Use Them by Matt Cronin at smashingmagazine.com