VB.NET制作excle表格能帮我解释一下里面的意思吗？

If Dir(Data) = "" Then
            File.AppendAllText(Data & Format(Now, "yyyy-MM-dd") & ".CSV", "  日期" & "," & "  时间" & "," & _
                               " 生产总量" & "," & "  不良数" & "," & "  不良率" & "," & _
                               "   备注" & vbCrLf, encoding:=System.Text.Encoding.GetEncoding("gb2312"))
        End If
大体的意思明白，File.AppendAllText（str1，str2）
我想知道里面"," 代表什么意思，以及后面的vbCrLf, encoding:=System.Text.Encoding.GetEncoding("gb2312")代表什么意义，我将后面的删除，程序照样运行。那他的作用是什么呢！