"Pandit," which simply means "learned man" in Sanskrit, is a title of respect in Hindu culture, and is the origin of the English word pundit. In writing it is sometimes abbreviated as "Pt."
Originally, the title of "Pandit" was bestowed on a Hindu scholar (almost always a Brahmin), who had memorized the Vedas (the main scriptures of Hinduism), not unlike the title of "hafiz" being bestowed in Muslim culture on someone who has memorized the Quran.
In more recent years, the title of "Pandit" has become more widely applied to anyone who has become a master in their particular field. The most notable example of this is in Indian Music, where masters of a certain instrument, such as sitarist Ravi Shankar have received this title through popular acclaim.
It is important to keep in mind that the title of "Pandit" is only granted to Hindus, and only to males. Master Indian musicians who are Muslim males are given the title Ustad instead, and female Hindu and Muslim master musicians are given the titles of "Vidushi" and "Begum," respectively.
Finally, another use of the word "Pandit" was in the region of Kashmir, where the "pandits" were a class of middle-ranking bureaucrats (although the etymology from Sanskrit of "learned man" was the same). It is from this usage that many Indians still bear the surname "Pandit," as in Vikram Pandit, the current CEO of the financial corporation Citigroup.