Vulcans were a humanoid species native to the planet Vulcan and one of the founding members of the United Federation of Planets. Vulcans were known for their strict adherence to following the path of logic and the suppression of emotions.
Once every seven years Vulcans undergo the pon farr. It causes a mental imbalance that sees them lose their emotional control making them prone to outbursts of emotion and even violence. To primary method to address this is by mating. If a Vulcan does not mate death can be the result. (TOS: "Amok Time"; VOY: "Blood Fever")
In the past the Vulcans were a violent and emotional race until Surak preached that the Vulcans abandon their emotions for following the path of pure logic. This was accepted by most Vulcan, though a minority rejected Surak's teachings and left Vulcan. (TNG: "Gambit, Part I", "Gambit, Part II")
By the mid-22nd century, the Vulcans and Andorian Empire were on the verge of war. Partly thanks to the efforts of United Earth relations between the two species normalised so that in 2155 both entered into talks to join the Coalition of Planets. (Star Trek: Enterprise)