皮 (pí) in a culinary context refers to the thin dough wrapper used to encase fillings in foods like dumplings and wontons. The full phrase 皮包 here means "wrapped in skin/dough." Outside of cooking, 皮 also means "skin," "leather," or "peel."
饺子的皮要擀得薄一点才好吃。
Jiǎozi de pí yào gǎn de báo yìdiǎn cái hǎochī.
The dumpling wrapper needs to be rolled thin for it to taste good.
馄饨皮比饺子皮更薄更透明。
Húntun pí bǐ jiǎozi pí gèng báo gèng tòumíng.
Wonton wrappers are thinner and more translucent than dumpling wrappers.
妈妈正在厨房里擀面皮包饺子。
Māma zhèngzài chúfáng lǐ gǎn miànpí bāo jiǎozi.
Mom is in the kitchen rolling out wrappers to make dumplings.