Guinan was a member of a race of listeners but her people were nearly wiped out by the Borg in the late 23rd century. The few survivors among her people escaped by spreading themselves across the galaxy.
Guinan spent some time on Earth prior to that planet's development of space travel. She lived in the Earth city of San Francisco in the year 1893, where she met writer Samuel Clemens, as well as future shipmates Data, Picard, etc., who had traveled back in time.
Picard was born on Earth in 2305. Jean-Luc was raised on a family farm in LaBarre, France, along with his older brother, Robert. As a boy, he enjoyed building ships in bottles. He failed in 2322 to gain entrance to Starfleet Academy at the age of 17, but was admitted a year later.
Jean-Luc Picard was appointed captain of the fifth Starship Enterprise in 2363, shortly after the ship was commissioned. Picard was abducted by the Borg in late 2366 as part of the Borg assault on the Federation. He was surgically mutilated and transformed into an entity called Locutus of Borg. As Locutus, Picard was forced to cooperate in the devastating battle of Wolf 359, in which he was forced to help destroy 39 Federation starships and 11,000 crew members.
The Borg implant themselves with cybernetic devices, giving them great technological and combat capabilities. Different Borgs are equipped with different hardware for specific tasks. Each Borg is tied into a sophisticated subspace communications network, forming the Borg collective, in which the idea of the individual is a meaningless concept. They exhibit a high degree of intelligence and adaptability in their tactics.
The Borg were responsible for the near-extinction of Guinan's people in the 23rd century. The first known contact between the Borg and Federation was in 2265, when Q transported the Enterprise-D out of Federation space into the flight path of a Borg vessel heading toward the Alpha Quadrant.
Source: The Star Trek Encyclopedia