Re: question.....
This is what what I have always thought
Pulao is rice cooked in a flavoured stock. the rice soaks up the flavour. Pulau/pilau is a uniform colour
Biryani is layers of par boiled rice, between meat or veg, or both. and then cooked till some of the flavour of the meat /veg soaks into the rice.
Biryani is a mixture of white and varying degrees of brown rice (due to how much of the meat mixture it has soaked up) and poss even yellow if things like saffron has been added to the top layer.
However I have noticed recipes that I wouldve called a version of pilau rice to be known as biriyani
I seem to remember that Pilau is a persion name and this type of way to cook rice has been used from persia/afghanistan down to what was northern India.
And Biryani is a moghul name for the elaborate moghul created dish.
(Moghul kings had chefs who had the time, money and ingredients to make elaborate dishes... and invented biryani and other recepies)