Sadly, you will find numerous folks out there who're of the opinion that pulao is exactly the same thing as biryani. This is not true. Despite the fact that both dishes are mainly rice based and originated in the Middle East or the Indian subcontinent, there are actually a few big differences that help to make each dish distinct. Here is how you can recognize the difference between the dishes:
1) Layering - Any time biryani is made the basmati rice should be cooked separately from the meat & masala. The rice should be cooked in it's own pot with an abudance of water and then it needs to be drained using a colander a little bit before it's fully cooked through. The rice then needs to be layered in a dish with the meat & masala (that has previously finished cooking). After the par boiled rice & masala are layered on top of one another, the entire dish is then baked in the oven.
In a pulao, the grains of rice are instead added directly into the masala and meat which has already been simmering in a pot (typically on a stove top). A bit of liquid is then added and the whole pot is closed with a lid and cooked right until the rice has absorbed the liquid and is completely cooked. This is what's called the absorption method of preparing rice (versus the draining approach used for biryani).
2) Level of Spice - Biryani is usually much richer in overall spice than a pulao. Overall the quantity of spices & aromatics incorporated into a biryani will be considerably larger than with a pulao. The important components which increase spice are red chili powder, garlic, ginger, and serrano chilis. Pulao however does not include as large a quantity of these ingredients and will also balance heat with other components such as raisins or nuts. Also, because of the layering in a biryani the amount of heat on each individual mouthful may actually fluctuate significantly. A first bite might be packed with masala and spice, whereas another might have much more plain white rice. This is very different from a pulao where the level of masala in a spoonful is made mostly uniform throughout the dish since the rice is boiled in the masala.
3) Easy of Preparation - Pulaos are normally less complicated meals to prepare as they're mainly done in a single pot and don't require the independent cooking and ultimate combination and stacking of rice and masala like a biryani does. Biryani will usually be used as a main component of a dinner as it is very hearty. Pulao, because of the ease with which it can be cooked (as well as its lightness relative to biryani), will generally just be a piece of a dish - not the primary course.
And so, I trust we've now clarified for you the differences between biryani and pulao. Enjoy your indian dishes!