Most of the user gets confused to differentiate between Integration and System testing. The basic difference as per my understanding is as follows:
Integration Testing: To validate whether applications integrated modules or integration with third party applications are functioning correct in terms of Data Flow or not. Its testing strategy is very different from system testing since in this we create test plan to keep in mind to check data flow from one module to another module or from home application to third party application and create test cases on the basis of created test plan.
System Testing: To validate complete developed application functionality (Functional and Non Functional) under same production like environment along with all other third party supporting applications. It generally performed when all releasing modules are completed and Integration testing has performed and no integration issue is left to fix.