Tara Maclay is introduced in the fourth season of Buffy The Vampire Slayer. Willow Rosenberg first met Tara when she was in college and Tara was part of Willow's campus Wicca group. During Tara's time in her Wicca group, she noticed that Willow was different than the other girls, and so Tara developed an interest in Willow. Later on in the series Tara and Willow are shown combining their powers to use telekinesis. It is shown that their power is stronger when in physical contact with each other. After this, Tara and Willow form a strong friendship and began practicing witchcraft together, performing very powerful spells. Soon Tara and Willow begin hanging out more and more as the season progresses and soon they form a lesbian relationship. Tara then becomes a regular on the show and joins Buffy's group of friends dubbed The Scooby Gang, and helps them fight against the forces of darkness.
Towards the end of Season Five Tara is assaulted and gets her mind sucked out by Glory, an evil Hell God who requires constant rejuvenation by sucking the brain power out of human beings. Tara is rendered helpless and is later found by Willow who goes after Glory in an attempt to kill her using black magic, but she fails and has to be saved by Buffy before Glory kills her. While Tara is in her childlike state she is cared for by Willow who later finds a way to cure Tara, but she has to be in physical contact with both Glory and Tara and then chant a couple words in order to return Tara to her normal state. At the end of season five The Scooby Gang goes after Glory for a final battle, during which time Willow jumps in and grabs Glory's hand and -- while holding Tara's hand -- she chants a few words and performs the necessary ritual, restoring Tara's mind back to full health.
In Season Six after Buffy is killed saving Dawn's life, Tara and Willow become Dawn's legal guardians. They move into the Summers house and take care of Dawn until The Scooby Gang resurrects Buffy and then Buffy becomes Dawn's legal guardian once again. During the sixth season Tara is shown to have made great progress since we first saw her in Season Four. She's seen using powerful magic spells and has become a smart and powerful witch.
Unfortunately, on May 7th, 2002 Tara is killed by a stray bullet fired by Warren Mear's in an attempt to kill Buffy right after Willow and Tara had just reunited after a fight. Willow takes her death the hardest and transforms into Dark Willow, in which she goes after Tara's killer, Warren, and kills him horribly before sending him to hell. But later Willow is restored back to herself after she finally just breaksdown and cries in Xander's arms.
Tara is later mentioned in Season Seven while a form of The First Evil attempts to get Willow to commit suicide. Willow sees through the deception when the First Evil begins to talk more in-depthly about Tara.
Tara was a skilled spell caster and performed a wide range of spells during her time on the show. She has successfully created fire, light, smoke, and has done minor blinding curses. Tara also has shown some ability of telekinesis, which, when she is in physical contact with Willow, is stronger than it would otherwise be (i.e. she and Willow pool their power by concentrating on moving the same object). An unusual ability she displayed is the ability to magically know something is wrong with someone and to sense the use of mental powers, which she did by "reading" a person's aura (such as when Buffy was possessed by Faith). Tara had a good knowledge of Latin and grew up riding horses. She rarely used the Internet because the preponderance of bad spelling depressed her.
Tara is shy, gentle and sympathetic. Amber Benson said this about her character; "She's quiet. It's mostly because she is shy, I think. I can identify with it in a sense, because I can be very shy too. It's almost like acting is an outlet for me that helps me to not be shy. I feel like Tara's the same way; her witchcraft empowers her and it forces her out of her shell."