What's Northwind.EmployeesRow Object

I am doing a tutorial where you use a templatefield in the gridview control to call a function. I don't understand the code for the function. What is the object Northwind.EmployeesRow? This is the tutorial I am doing. Tutorial 12: Using TemplateFields in the GridView Control And this is the code for the function.

Protected Function DisplayDaysOnJob(ByVal employee As Northwind.EmployeesRow) As String
If employee.IsHireDateNull() Then
Return "Unknown"
Else
' Returns the number of days between the current
' date/time and HireDate
Dim ts As TimeSpan = DateTime.Now.Subtract(employee.HireDate)
Return ts.Days.ToString("#,##0")
End If
End Function