They can never get enough of any food or liquid to feed themselves and are always hungry, always thirsty. In another realm are the Green Giants which, unsurprisingly, are green and giant-size. They have fangs and big eyes, like Titans - big, ugly, monstrous, warrior types of beings. Hungry Ghosts and Green Giants symbolise the two realms of desire and aversion, those movements of the mind that fight, chase, want and need. We chase things for reassurance.
People find reassurance in many different areas - food, for example.
Eating sweets is emotionally reassuring. It appeases our insecurity. We seek after praise, too. To be attractive is reassuring because I am then worth something. I need this reassurance continuously because I am a separate entity - a little me who feels vulnerable.