Help in conceptualizing some of the concepts of DSP involved in gnuradio

Hi everyone ,
First of all i am a newbie in this domain and really apologize for
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

,starting with the “understanding DSP by R.Lyon” …
Can someone explain what really are the steps actually gnuradio along
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 ,
please someone explain me the analog and DSP part of the actual process
tuning and setting a frequency.