What is the difference between a POS and cash register?

When you want to do more than ring up sales, you know it’s time to move from your cash register to a cloud-based POS system. While a cash register is a great place to store your…well, cash, a POS system acts an additional employee (or several employees) to your business. From helping you manage inventory to tracking customer preferences, managing loyalty programs, offering the tools to create a more personalized customer experience, tracking employee sales performance and giving you the data to run reports that will help guide your business decisions, a POS becomes a key component of any commerce or hospitality business.

https://www.lightspeedhq.com/blog/2015/06/what-is-a-pos-purchase-and-other-pos-term-clarifications/