Warning: Wikipedia contains spoilers.
Throughout the series, Ben Sisko is in charge of the Bajoran sector, a new frontier for the Federation. As the series begins, Captain Jean-Luc Picard briefs Sisko that Bajor needs help to regain what it had lost in the Cardassian Occupation of their planet. By chance, Sisko and his crew discover a wormhole to the Gamma Quadrant, and the aliens living therein - the Bajoran Prophets. This discovery leads the Bajorans to acclaim him as the Emissary of the Prophets, a role about which Benjamin is decidedly ambivalent through at least the first part of the series.
As the storyline evolves, however, Sisko comes to accept his role, and discovers the part the Prophets are to play in his life, particularly as the Prophets intervene in the Dominion War and gradually reveal his destiny as being integral to that of Bajor. In fact, it is finally revealed that his mother, Sarah, was the incarnation of a Prophet - he was born to serve as the Emissary.
In the end, his destiny comes to fruition as he confronts Gul Dukat, possessed by a Pagh Wraith - the antithesis of the Prophets - and destroys him. At this point he is assumed to live with the Prophets.
Throughout the series, Benjamin distinguishes himself as a military commander during the course of the Dominion War, against threat forces as varied as the Dominion, the Breen, the Klingons, the Romulans, and the Cardassians.
Benjamin is the son of Joseph Sisko, a chef in New Orleans. Ben is the father of Jake Sisko and the widower of Jennifer Sisko, who was killed at the Battle of Wolf 359 while Benjamin was the first officer of the U.S.S. Saratoga. During the last season of the series, Benjamin marries Kasidy Yates, who at the end of the series is carrying his child.