Double or multi exposure is a technique used by photographers that uses layering in order to combine 2 or more photos into 1 to create an almost ghost-like affect. This can be done on film cameras by inserting used film back into the camera and taking photographs over the top of the film, or in Photoshop by layering images and adjusting the opacity.
Double Exposure moodboard
Double exposure inspired photoshop development
To edit these images I layered 3 images over each other and adjusted the opacity in order to fade out the images as they get further from the original image. I also used the monochrome filter on one of the layers to create a ghost-like affect.