Difference between Integration and System testing

System testing -

1) It is high level testing and always starts after Integration testing
2) For this testing, complete system is configured in a controlled environment and test cases are developed to simulate real life scenarios.
3) Purpose of this is to validate the application's accuracy and completeness in performing the function as per the requirement.

Integration Testing -

1) It is a lower level testing where testing is done to ensure that the interfaces between the components working as per the requirement.
In every application we intially implement small Sub-functionalities and integrate those...to make it a big functionality...so it is necessary to verify dependencies between the small sub-functionality.