Two features are characteristic of their physical appearance: eyebrows that are arched and run upwards and ears that form into a point at the top. Their hearing sense is very sensitive. Their culture is based on logic and reason and they control their emotions to a point where they will not even notice them. The mating drive of the Vulcans is known as pon farr and overcomes them approximately every seven years. Vulcans must then mate with someone they are emotionally connected with or they will die or become insane.
For further information, see the Wikipedia entry http://en.wikipedia.org/wiki/Vulcan_(Star_Trek)