The Bajoran Wormhole was inhabited by aliens known to the Bajorans as the Prophets. The Prophets experience time differently from humanoids, allowing them to see past, present, and future events simultaneously.
As the only means of travelling between the Gamma Quadrant and Alpha Quadrant in less than several decades, the Bajoran Wormhole was a critical choke point in the Dominion War. The Dominion had superior military assets in the Gamma Quadrant, but they could not bring those assets to bear while the Federation controlled the Alpha Quadrant end of the wormhole.
Some Trekkies have tried to diminish the strategic importance of the Bajoran Wormhole in order to claim that the fleets of hundreds of starships used in military actions aimed at controlling it represented small side fleets instead of the bulk of the fleet assets available to the combatants.