A payroll provider is a company that your employer uses to process paychecks, W2 and more. Your payroll provider is typically where you log in to view your paystubs online.
Most commonly seen payroll providers include ADP, Paychex, Paycom, Paycor, Paylocity, SAP SuccessFactors, Gusto, UltiPro, Workday, Zenefits, etc.
For government organizations, we typically see payroll providers such as MyPay, myEPP, Employee Express, etc.