府上 is a polite, honorific term for 'your home' or 'your family' — used when speaking to someone with respect, similar to 'your residence' or 'your esteemed home' in English. It's a formal expression, typically used in conversations where you want to show deference to the other person, such as when visiting or asking about their family. Do not use it for your own home; use 寒舍 or just 家 for that.