Square is a mobile payment system that allows businesses to accept credit card payments directly on their smartphones or tablets. It started as an app called Card Case that let users find nearby businesses and pay tabs, but has evolved into Pay With Square, which displays nearby businesses on a map and their details. Square works by having the business register their account using Square's payment processing system. While currently only available in the US, Square plans to expand internationally in the future. Common users of Square include small businesses, food trucks, retailers, and other merchants looking for an affordable way to accept credit card payments on mobile devices.