I am Learning Pic Basic, and I took ADC Sample code from melabs. I woul like to understand the following LCD Defination

Define LCD registers and bits
Define LCD_DREG PORTD
Define LCD_DBIT 4
Define LCD_RSREG PORTE
Define LCD_RSBIT 0
Define LCD_EREG PORTE
Define LCD_EBIT 1

Lastly

adval.highbyte = ADRESH ' Move HIGH byte of result to adval
adval.lowbyte = ADRESL ' Move LOW byte of result to adval

Will be thank full if Someone Helps me