Acne is a lesion formed by hyperkeratosis of the follicle funnel. It is a clinical manifestation of acne. There are generally two types of acne: open and closed. The cause is abnormal keratinization of the follicular sebaceous gland ducts, keratinization of the follicular opening, failure of epithelial cells to shed normally, making the follicular opening smaller, and the shed epithelial cells and sebum accumulating in the follicular opening. In common parlance, this means that the pores are clogged. Open pimples generally refer to blackhead pimples. Closed pimples are generally referred to as whiteheads. So when you say “closed mouth” on the internet, you are referring to closed pimples, also called whiteheads, which is just a type of acne. Another way to say it is that acne is the Chinese name for acne, which refers to acne in general.