*pushes up glasses* Well the Triforce is sort of this magical artifact in the Zelda universe. When the three goddesses created Hyrule, they departed for the Heavens. At the spot where they left Hyrule and entered the Heavens, the Triforce was formed. Well, the Triforce happens to hold the power to basically grant the wish of whoever touches it, be them good or evil. The three parts of the triforce represent courage, power, and wisdom. The only way to have FULL control over the triforce is to obtain all of these virtues (and/or be pure of heart.. not entirely sure here).
This wasn't as easy to explain as I thought it would be, lol.