Testing the behavior of the whole software/system as defined in software requirements specification(SRS) is known as system testing, its main focus is to verify that the customer requirements are fulfilled.
System testing is done after integration testing is complete. System testing should test functional and non functional requirements of the software.
Following types of testing should be considered during system testing cycle. The test types followed in system testing differ from organization to organization however this list covers some of the main testing types which need to be covered in system testing.