hunger is your body saying it needs food.
a craving is you saying you want a specific kind of food.
cravings don't have to be for unhealthy food. i was craving apples last week for example. other people crave berries or milk or even vegetables. a craving just means you want something specific. giving in to every craving every time might be an issue, but most people do give in to at least some cravings and it's not a big deal. let's say we're craving pizza. having an extra large domino's isn't a great way to cave in to the craving. but taking a flatbread, layering on tomato slices, herbs, cheese and vegetables is. or some people might do a cauliflower crust or use a portabella as the crust, layer on tomato, spices, cheese and veggie toppings.
not eating for three days is not healthy. if you aren't getting any hunger signals while you skip food for three days trying to wait out a craving, something in that feedback loop is messed up and you may not want to trust it, at least for the short term.
-google first. ask questions later.