An integration is when you take one software and add it into another so that you can track and use them in tandem. So, say you have a customer loyalty system that you use, and you want to be able to add it to your POS system to sync purchases with loyalty rewards. Either your retail point-of-sale system will have a built-in integration that allows you to seamlessly integrate your loyalty program, or you can work with a developer to create a custom API to combine the two software.