Layer Property defines the blend method between the insert image/text and the photo. You can set it at the page of 'Layer' when you add image or text.
Normal: Copy each pixel to dest image. It is the default mode.
Screen: Add pixel value to dest image.
Light Only: Only pixel which is lighter than dest pixel will be copied to dest image.
Dark Only: Only pixel which is darker than dest pixel will be copied to dest image.
Difference: Copy the result of XOR operation to dest image.
Brightness: Replace the brightness of dest image with the brightness value from the layer.
Color: Replace the color with of dest image with the color value from the layer.
Other Modes, just same with Photoshop and other image processing software.
