Curry is considered the ubiquitous Indian spice blend. In reality - it is a British invention trying to capture the traditional flavors of India into a single blend. There are as many different ways to blend curry as there are Indian families creating it. The blend is very family-specific, and sometimes guarded with great enthusiasm.
Curry is a spice blend. In the basic form, all curries tend to contain 6 core spices in varying proportions. Cumin, Coriander, Cardamom, Cinnamon, Fenugreek, and Nutmeg. The basic curry spice blend containing just the 6 spices is called a "SWEET CURRY". Not because of a sweet taste, but because the flavors tend to be sweeter to the tongue and there is no heat. A common addition to most curries is TURMERIC. This flavorful and colorful root is bright yellow and contains massive amounts of the active ingredient "curcumin". (One would think that cumin would also contain this compound, but no. In many languages - cumin is known as Jeera, but I digress.) Turmeric is a wonderful anti-oxidant, anti-inflamatory, and all-around positive for your health. In fact, most of the ingredients in curry are medicinal by nature in addition to having great flavor.
Vindaloo Curry is known for it's spicy presence, brought out by the very liberal use of chiles celebrating their capsaicin content which tends to be higher in chiles from Asia and India. Madras, another hot curry, does use chiles also, but tends toward the very wonderfully packed heat of Pepper (piper nigrum). The Malabar, Madras, and Tellicherry regions of India are absolutely famous for their wonderfully rich, fragrant, and powerfully pungent peppercorns.
Making a curry blend at home will always result in a more deep and nuanced product than can possibly be produced in bulk. Taking the right mix of fresh spices, and toasting them in a pan until the oils begin to cause the seeds to swell will improve the flavor dramatically. A quick grind of the toasted seeds and then toss into the dish to marry all the flavors together. The flavor profile of commercial spices can be enhanced by a simple toss of the blend into a pan to simmer for a moment with butter or olive oil, depending on your diet.
Cooking with curry is good, and good for you.