In very broad terms, system integration is the process of connecting different sub-systems (components) into a single larger system that functions as one. With regards to software solutions, system integration is typically defined as the process of linking together various IT systems, services and/or software to enable all of them to work functionally together.
The main reason for organizations to use system integration is their need to improve productivity and quality of their operations. The goal is to get the organizations various IT systems to “talk to each other” through the integration, to speed up information flows and reduce operational costs for the organization. But system integration is not used only to connect an organization’s internal systems, but also third parties that the organization operates with.