Question about 4WD/AWD

I think I am going to get a 4 door Ultimate Sahara and it says it's 4WD/AWD. Now I know I can shift it into 4WD but I am confused about the AWD.

Does it mean that if my Jeep needs to it will automatically put it in AWD or is it always AWD?

Update: Thank you for everyone's input! Fill free to still respond - I will read them! But from what it seems like is that I don't have the Auto/Part time 4H on the shift therefore don't have Jeeps Version of AWD.