Yes, a DC-DC buck converter with a 5V output.

OOk, i try to arrange that from the market

 

but this would help me or not? or tell me any other easy way how to change 12 volt to 5 volt for usb charging for this current project? what should i do?

 

or tell me any other easy way how to change 12 volt to 5 volt for usb charging

You could use a linear regulator, but it would be inefficient and run hot.

 

You could use a linear regulator, but it would be inefficient and run hot.

so alec , tell me again, what should i do, what you call it exactly that dc dc buck converter. i am going to the market now. can i add this buck converter in my project?

 

what you call it exactly that dc dc buck converter

I'd call it a switch-mode 12V to 5V converter.