(covers information from several alternate timelines)
Temporal shielding was a type of force field technology developed by the crew of the USS Voyager in an alternate timeline in 2374 in order to defend themselves against Krenim chroniton torpedos, which had the ability to penetrate conventional shields due to being in a constant state of temporal flux.
In this timeline, Voyager came under near-constant attack upon entering a region of space in the Delta Quadrant which the Krenim controlled. Determining the exact temporal variance of the torpedoes, Lieutenant Commander Tuvok and Seven of Nine were able to develop temporal shielding by matching Voyager's shields to the variance, and matching their deflector array to the inverse of the variance. The newly-modified shields were effective in defending against the chroniton torpedoes, as well as insulating Voyager from the changes to the timeline initiated by Annorax, a Krenim scientist who was using a massive weapon ship to erase objects from history.
Voyager's temporal shields produced a level-9 temporal disruption, which threw off Annorax's calculations, causing him to inadvertently revert the Krenim Imperium to a pre-warp state. Intercepting them to investigate, Annorax attempted to erase Voyager from history, but was unable to penetrate their temporal shielding before Voyager managed to escape. Later, forming an alliance with the Nihydron and the Mawasi, the Voyager crew provided them with temporal shields as well, allowing them to assemble a fighting force to take on Annorax. Engaging the weapon ship in battle, two Mawasi ships were erased from history when their temporal shields were overwhelmed. Captain Janeway subsequently ordered all ships to take their temporal shielding offline, and used Voyager to collide with the weapon ship. The weapon ship's temporal core ultimately destabilized and initiated a temporal incursion within the ship itself, erasing it and all of the damage done to the timeline by Annorax from history. (VOY: "Year of Hell", "Year of Hell, Part II")