our shop; our store
Humble term used by a business to refer to its own shop or store when speaking to customers or outsiders.
Our store is currently holding a sale.
All products at our shop come with a quality guarantee.
当店 is the standard polite way staff refer to their own store, while 弊店 is a more humble version typically used in formal written correspondence.
Compound of 弊 (humble prefix for 'our') and 店 (shop, store). The prefix 弊 is used in humble business language.