How ADC value stores inside ADRESH and ADRESL register for pic16f877a

I am trying to understand how adc works and also trying to make an ADC function

If the result is Right justified can anyone describe how the adc value stored??
And IS ADRES is a valid MCU register??

If the adc value taken is 563. In binary it is 1101010101.
Then the lower 8 bit stored in ADRESL register (8 bit register).

That is 01010101 goes to ADRESL register (8 bit register).

and the upper 2 bit i.e 11 goes to bit0 and bit1 of ADRESL respectively
but is some example of...

How ADC value stores inside ADRESH and ADRESL register for pic16f877a