Cats are obligatory carnivores, so they get their nutrients from animal protein. If your healthy cat shows an interest in peanut butter and they’re not on a specialized diet for a particular health condition, they can have some peanut butter in moderation—but it won’t offer them any nutritional benefits. If you’re going to give your cat peanut butter, you should only dole it out very occasionally and in moderation. Think of it like a treat.
A word of caution, however: Be sure to read the label before offering some to your cat. Some peanut butters contain a sweetener called xylitol, which is toxic to cats. Use a peanut butter with minimal ingredients and additives.