https://www.entrepreneur.com/article/360670

In 2009, a then small startup called Square (which was co-founded by Twitter's Jack Dorsey) proposed a pretty disruptive idea: What if the cash register became obsolete? After all, clunky point of sale systems have proved to be a major source of frustration for small businesses, who were forced to use unintuitive technology that made even the simplest of tasks, like editing orders or printing out a simple receipt, difficult. Its alternative to the machinery that had dominated brick-and-mortar for the past few decades? The Square Reader, a small device that attaches to a smartphone or tablet and allow users to easily swipe their debit and credit cards to get their receipt immediately emailed to them. And thus began Square's journey to simplifying and streamlining tasks for businesses across the globe. 

While many of us have already interacted with the Square Reader (there are over three million merchants who have used it to process over $12 billion in transactions a year), fewer have tried out Square's other offerings. This includes Square Capital, Square Payroll, Square Cash, and Square Invoices. Consider the latter product an especially solid secret weapon for small and large business owners, freelancers, entrepreneurs, or anyone else who needs to manage their payments and recurring invoices.