This is a way to add images with a caption. The images have all the same width, and the height is regulated by the code.
Images and caption are popped into a container, here .masonry-css-item, and then all those containers are placed in a column in the .masonry-css wrapper. The Multiple Columns feature has been used to form the display. It is a good thing to think about balancing the column height, so you may want to move your images around a bit.
This component does not work well in IE11, the image size gets cut off a bit.