@jaynspain focus stacking is mainly used in macro photography to achieve a larger depth of field. You take multiple shots each with a slightly different focus point. You can do this either by keeping the camera in place and turning the focus ring (use manual focus and a prime lens (no zoom)) or you can use a macro focus rail (expensive). You then combine the images (I used as many as 11 I've heard of people using 100) in Photoshop or a dedicated software application
I like the deep red, warm colour. Thanks for the info above. Must really have a go, haven't got a macro lens, but I assume my 50mm lens will be able to do it.