your store; your shop
Honorific term used to refer to the listener's or reader's store or business establishment. Common in formal business letters, emails, and polite conversation.
I wish your store continued prosperity.
Thank you for your assistance at your shop the other day.
当店 refers respectfully to one's own store, whereas 貴店 is the honorific term used to refer to the listener's or customer's store.
Compound of 貴 (ki, 'honorable, your') and 店 (ten, 'store, shop'). The prefix 貴 is commonly used in honorific business terms.