What makes a pilaf? Cooking the rice in butter or oil (and often onions or other vegetables) before adding other ingredients, at the very least a flavorful liquid like stock. Yellow rice is a form of pilaf, as is biryani, as, one could argue, is paella. It’s a universal technique, and I try to cover many of the bases here. But the key, the aspect they all have in common, is the sauteing of the rice at the beginning of cooking. That little step makes a world of difference, and pilaf is truly one of the great gems of basic home cooking (risotto, is more widely praised, and perhaps better known, but it is not better, and it’s a little more challenging).
Other than that, much is up for grabs: The rice may be long- or short-grain (personally I think of basmati as the default, but short-grain has its own charm, and in some instances it’s better), the liquid may be stock or wine or dairy or nondairy milk (or even yogurt), and the herbs, spices, and solid ingredients can all be varied according to your desires. To make what you might call Golden Pilaf, heat a large pinch of saffron threads (or a teaspoon of ground turmeric, which isn’t as good but is a lot cheaper), with the stock.
Even brown rice is fair game, but the technique is slightly different; see Brown Rice Pilaf with Two Mushrooms.
One other thing that is really great about pilaf: within limits, it can be reheated successfully, either in the microwave or on the stove. Just add a little water first, cover it, and reheat gently.