There are some reports that there are over 800 breeds of cattle that can be found all over the world. They are different in terms of the climate wherein they can live. There are also some that are able to live depending on why they are specifically bred by human beings. For instance, some are used for their milk.
There are some that are almost the same that people get confused with their breed. There are also some that are obviously different although they are under the same category. Learning more about cows can be very interesting especially if they are very useful to you and your needs.
Actually, the word 'cow' properly includes the adult female of various species, such as moose, elephants and sea lions, but you probably mean our most common bovine when you ask about the cow. They are the most common domesticated ungulate (hoofed) and are found all over the world: India, China, South America have the most.
Basically, all species of cow come from the two main types: hump backed and without hump. Cattle breeds are numerous, probably around 800, and if you would like to see a long variety of them, try out the International Cattle site. To be more specific, you might want to look just at dairy cattle or just at beef cattle. They are different lists of types and it's quite nice to get a poster with pictures of each breed.