[Discuss-gnuradio] Help in conceptualizing some of the concepts of DSP involved in gnuradio

[anil ph]

Hi everyone ,
   First of all i am a newbie in this domain and really apologize for any sort of illogical mistakes or questions asked from my side.
I am tracing gnuradio code so as to understand the gnuradio and the DSP involved in that ... I am reading the gnuradio suggested reading order 

http://gnuradio.org/redmine/wiki/1/SuggestedReadingOrder 

 ,starting with the "understanding DSP by R.Lyon" ....
Can someone explain what really are the steps actually gnuradio along with usrp executes when we tune or set 
a frequency using tune() function in gnuradio.

Example : if i provide 920MHz to the usrp from my python script in usrp_rx_cfile.py ,
please someone explain me the analog and DSP part of the actual process of tuning and setting a frequency.

Thanks.
Phenomenon.