Define LCD registers and bits

1 Define LCD_DREG PORTD
2 Define LCD_DBIT 4
3 Define LCD_RSREG PORTE
4 Define LCD_RSBIT 0
5 Define LCD_EREG PORTE
6 Define LCD_EBIT 1

-Correct me if I am wrong, I understand Line 1 & 2
Line one means the LCD shold read from port D, Line 2 mean 4 bits
Should be connected LCD i.e RD0, RD1, RD2 & RD3
What I dont understand is line 3, 4, 5, 6. I am using pic16f876 & doest not hv pot D & E thats why I want to adapt this code

Thanks