Perishable is a term for a product that has limited time to sell. A product like meat, fruit, and most fresh food will have a shelf life and you have to sell the product before the shelf life expires. Some preservation techniques can help to extend food products like freezing or curing them.
Room night of a hotel or any rent product is also considered as perishable since you can't store the rent time and sell it another day. So, every unoccupied room is treated as expired food. Unlike food products, room nights for the hotel can't be preserved. There are other strategies to maximize the revenue of rent products such as overselling or selling promise/reservation.
