What app is Busd?

Could you please clarify what you mean by "Busd" as an app? Are you referring to Binance USD (BUSD), which is a stablecoin pegged to the value of the US dollar? BUSD is not an app in the traditional sense, but rather a cryptocurrency token that can be used on various blockchain platforms and exchanges, including Binance. It is designed to provide a stable and reliable store of value for cryptocurrency traders and investors. If you are asking about a specific app that utilizes BUSD or allows you to manage your BUSD holdings, there may be several options available depending on your needs and preferences.