That site looks like it is using something like Web Album Generator. I haven't used this in many years, but I believe it is pretty simple. I thought Adobe had an easy free one also, but I can't seem to find it.
These types are pretty easy to use, you just make the album at your pc, then upload the files. The other types of galleries do all the work for you, makes thumbnails, others can upload files and add to the gallery, etc. People can add comments.
Good luck finding one you like.