If you use different senses the body has, like smell, feeling, touching, tasting, all these things help to create a mental image because if you have already experienced what you are mentally trying to imagine, using those senses help you to make that mental image appear.
Example - Say you went to an amusement park when you were little and you are trying to remember the different types of food that you ate there. You could walk past a vendor or bakery and some of the smells coming from there might help you to remember the different foods they had at the amusement park. You would be using your sense of smell to help you create that mental image of the foods you once had.
