Cisco IOS Boot System Image

Hi Rene,
Thanks for your nice article …
I want to be more clear about What is the job of configuration register ?? My understanding It will instruct router where have to search the IOS . Please make me clear on it once again dear .
What will happen if we set 0x2101,0x2102 and 0x210F ?? a little bit confusion here .

Also want to know when we will set 0x210F and put command Router(config)#boot system tftp c2800nm-adventerprisek9-mz.151-4.M12a.bin 192.168.1.2 . Then the IOS will be load from tftp to RAM directly or Load in Flash first . Confused that you have write the section Booting IOS image from network

br//zaman