Guinan was the mysterious bartender at Ten Forward, the lounge aboard the USS Enterprise-D. She was well known for her wise counsel which had proven invaluable many times. She was an El-Aurian, a race of "listeners" who were scattered by the Borg. Q, however, once suggested that there was far more to Guinan than could be imagined. One can only speculate as to the meaning of this.
Guinan was born some time before Earth's late 19th century on the El-Aurian homeworld. When she was a child, she had a Tarkassian razorbeast as an imaginary friend. When she was troubled she'd talk to it, and she enjoyed just curling up on his warm belly. As she grew older, she found that she talked to it less and less, but the idea always remained.