As with many animals, your cat's stomach is the most vulnerable part of his body. If he is exposing it to you without acting or sounding aggressive, it is because he trusts you completely. The exact reason he wants you to rub it can vary.
For some cats, rolling over and asking for a tummy rub is a form of greeting. According to PetAssure, this type of greeting is rare but is the ultimate compliment from your cat. Asking you to touch his stomach, the most vulnerable part of his body, conveys total trust.
According to WebMD Pets, cats may stretch out and roll over when they are happy and content. Wanting a belly rub can be a sign of how happy your cat is.
Cats also roll over for tummy rubs when they are relaxed. If your cat stretches out beside you on the couch or in your lap and wants a belly rub, it can also be because he is relaxing right along with you. If he falls asleep this way, it is a signal that he trusts you so much he feels no need to protect himself.
Cats may also want to play when asking for a tummy rub. He might be feeling frisky and in the mood for some harmless roughhousing, like the kind he used to engage in with his litter mates (and might still engage in with other cats, if you have any). You probably know by now how rough your cat likes to play and if it's safe to subject your bare hand to a wrestling match with him.
Leslie Carver has been a professional author since 2009. Her work appears on multiple websites. She has an associate's degree in English with progress toward her bachelor's at the University of Tennessee, Knoxville. She has been awarded an Outstanding Student Award in English and twice nominated for creative writing awards.