The masking tool is used to "cut" an image into the shape of an icon.
To do so, you need to select an single-colored icon and any image (image from Piktochart's Photo Library or your own from Uploads).
To select the image and icon together, hold the shift key as you click to select.
Next, click on the mask button from the menu at the top.
Double-click to reposition your image within the icon. Drag to change its position or use the handlers to resize your masked image.
This tool is great for adding fun shapes to your images rather than having it just appear as a boring old square.