An Enterprise system is an interconnected patchwork of applications. This usually centres around a mix of ERP systems (like SAP), with industry specific applications, then a range of functional systems such as CRM and others. For the nitty-gritty, you can read Johnny's reflections on Application Integration.
Linking up Businesses with LabCom
Most processes are handled inside enterprise's big systems. On occasions, it's necessary to write original pieces of software to solve business problems. For example our range of chemical sample tracking systems, LabCom, merge the data management of related organisations, ranging from field data collection (on tablets), asset and client list integration with other Enterprise systems, interacting with the data in third party laboratories, and sending automatic alert emails to the final clients. That's three types of organisation integrated with one system.
On other occasions data from disparate systems needs to be marshalled following a business event. For example, gathering and creating paperwork for financial institutions, to allow last minute response to market conditions and competitor activity.