HI friends when i make a call to a particular number from noika phone and in between i press option button and there i see one keyword "send DTMF".
i know it is "dual tone multi frequency" and it send some signals to service provider when you press any key on the phone. But i don't know why exactly it is used for\?

What are the advantages of it and why it is used, whats the real purpose and how it will help in and in what matter?
Thanks
Regards