This ADE register lets you to set if a input pin should have the analog capability or not.So for AN0 to AN31 pins you need to set each bit corresponding to each pin in the order whether it is analog input or digital input/output because by default the value of ADE register is 0xFFFFFFFF which means Analog input. So when you want to use the pin as Digital input/output you need to reset the corresponding bit for the analog port.
However the GPIO bit-band capability allows you set /reset each bit by writing to their corresponding bit-band register which is the line of code you have pointed out.
Thank you very much. Now I get the point.