Vulcan
Vulcan has always been a world shrouded in mystery, both within the Star Trek universe and without. Information given in the series has not always been consistent, and attempts to unify it such as Diane Duane's Spock's World aren't canon. The official Web site StarTrek.Com offers a fragmented article on Vulcan that culls facts from all five TV programs. (Very diplomatic.) Articles in the various Encyclopedias contain a lot of "maybes" and "reports indicate . . ."
So what do we know? What can we be sure of? What else but: Spock. Much of what is below is taken from observations of Trek's first legendary Vulcan, with respect of course for the later series. Nimoy provides some insights himself in the 1995 book I Am Spock. Though the planet’s "mystery" can be a setback, it also adds appeal, and the culture resonates strongly in the imagination.
Climate. As its name might indicate - taken from the Roman god of the forge - Vulcan's surface is hot, dry, dusty, and rocky in spots. It has two suns and appears red from space. The inhospitable climate is accountable for their path of biological and cultural evolution, in light of theories directly linking a people's development with their environment. (See Jared Diamond's Guns, Germs, and Steel: The Fates of Human Societies - I'm sure he means that in Kirk's "everyone's human" sense.)
Biology. Though humanoid, Vulcans can be recognized by outward features such as their pointed ears and think, slanted brows. Their copper-based blood gives their skin a greenish cast, and the "bowl haircut" has endured centuries. Vulcan skin tone ranges from light like Spock's family to dark like Voyager's Tuvok and the priestess in The Final Frontier. Their internal arrangement differs from humans, as McCoy points out. The lungs are larger, pushing the heart down to where the human liver is found. As Nomad observes in The Changeling, Vulcans are "well-ordered" and their physiological efficiency means they can go without food or sleep for weeks. (As in The Paradise Syndrome.)
Through Spock we realize Vulcans have heightened sensory perception by human standards. His ears intensify sound and an inner eyelid shields him from blinding light in Operation - Annihilate! He demonstrates great physical strength as well as psionic powers on numerous occasions. Though all Vulcans have the capacity, it takes study and discipline to achieve the famous mind meld and employ similar skills for the lighter mind touch. Spock and Tuvok are such practitioners.
Millennia ago, Vulcans were a race ruled by their passions, but have since learned to suppress these impulses. The biological outcome is the pon farr, or the male mating drive, which occurs every seven years. Thus Spock must return to his planet to take a mate or die trying.
History. Life on Vulcan began as a struggle for survival, with its people fighting over the limited resources. Tired of endless bloodshed, thinkers like Surak emerged, who would preach a philosophy of peace and reason. Though the process was slow, the whole planet came to realize Surak's logic and have been guided by his principles ever since. Those who disagreed formed the Rihannsu group, and departed for Romulus.
First Contact with humans was made in 2063, when a passing Vulcan scout ship detected Zehram Cockrane's warp signature, a sign Earth had developed sufficiently for communication. Later, when the Federation was created, Vulcan became a founding member. Humans were relieved to have such peaceful and cooperative partners. The Vulcans' IDIC principle, or "Infinite Diversity in Infinite Combinations" embodies Federation ideals. Vulcans have continued to serve in Starfleet since Spock's time, though their positions are not always predictable. Valeris in The Undiscovered Country joins a conspiracy to disrupt the Khitomer peace conference, while Sokona is a member of the rebellious Maquis. As Voyager's Captain Janeway says when chiding Tuvok for stealing alien technology, " Logic can be used to justify anything. That's its power, and its flaw."
A Vulcan's Life. Life means following the path of pure logic, eventually achieving the kohlinar and becoming free of emotion. Though knowledge is most prized, a series of rituals for young Vulcans develops mind and body, requiring strength and discipline in both. While the early rituals remain mysterious, much is known to us of the kun-a-ta-kali-fee, or marriage ceremony. Vulcans are bonded with their mates at an early age, and return when the pon farr drives them home. There the woman may accept the man as husband, or have him fight for her, a throwback to Vulcan's martial past.
The Vulcan Science Academy is a popular choice for young students, though beginning with Spock, some choose Starfleet. Interaction with illogical humans and many kinds of aliens makes Vulcan detachment difficult, but many see it as a positive challenge and broadening experience. Vulcans can also choose a monk-like existence in their mystical hierarchy. Vulcan's rulers are often matriarchs (like T'Pau and T'Lar), capable of overseeing important rituals and performing functions like the fal-tor-pan in The Search for Spock.
Ideally all Vulcans strive for pure logic - by several means - though many must accept that it is not feasible given their life choices. Accepting one's unique circumstances, opportunities, and limitations becomes as important as fulfilling a society's expectations. Realizing this is a Vulcan's greatest achievement.