This is a simple modal gallery. The images get displayed in larger, one after the other, in one and the same modal 'frame'. The images' title tag is used to show the title below the images.
It is possible to have images of different size and shape, but it will look better if they all are the same. If you do want to use images of mixed sizes, you can add a second class name to them, calling them e.g. square-img, portrait-img etc. Portrait-orientated images may need to have the height limited.
You can add or subtract images without having to change anything in the settings. When adding images, just give them the same attribute that the others have, and a title.