Refers to animal skin processed for use, often in industrial or commercial contexts. More formal than 革 (かわ).
This bag is made of genuine leather.
Use a special cream to care for leather goods.
This factory processes cowhide into leather.
That shop sells high-quality leather goods.
皮 refers to raw, unprocessed skin or peel, while 皮革 specifically means leather that has been tanned and processed for use.
Compound of 皮 (ひ, 'skin, hide') and 革 (かく, 'leather, tanned hide'). The reading かく is the on'yomi of 革.