Important Notice: Our web hosting provider recently started charging us for additional visits, which was unexpected. In response, we're seeking donations. Depending on the situation, we may explore different monetization options for our Community and Expert Contributors. It's crucial to provide more returns for their expertise and offer more Expert Validated Answers or AI Validated Answers. Learn more about our hosting issue here.
They are pores which have holes in their walls that allow gasses or liquids to flow to and from other pores. This is similar to the structure of sponges. An example of closed pores is bubble wrap packaging: gasses or liquids can not enter or exit the pores (i.e., the bubbles) without breaking them.
