What is meant by segregation of duties 'Specify for accounts department"?

Segregation of duties is an internal control concept that requires different people to complete different parts of a task. The main objective is to prevent a single person from defrauding the organization. A secondary purpose is to catch and prevent serious errors from occurring. The concept of Segregation of duties can be difficult to achieve while maintaining optimal efficiencies throughout the entire process.  i.e. :

Separation of duties requires that the person responsible for balancing the payroll account must be different from the person issuing the payroll checks.

It means two concept , First Operation , meaning to make every one hold part in a company , Second Audit and control , meaning not to let one person be the Key for any Job , but make sure that not one have all the control for the company.