Double Exposure Effect using Photoshop Software
Double exposure is two partial exposures combined to create one complete exposure.
In Photoshop you can set the layers to multiply mode, which fuses the layers together and enable the opacity of the images to be altered and be overlaid over another.
There are many different ways and styles to create a double exposure in Photoshop, above video showcases a simple solution which helped me understand the effect and sparked my imagination into experimenting with different images and photoshop adjustment tools. Have fun and play with the different exposure layer tools inside the photoshop layers window.