From the Star Trek Online Site:
Starfleet, the Klingon Defense Force, and the Romulan Republic have all kicked up their recruiting efforts. New captains in any of these factions will be known as Delta Recruits, and they bring with them the knowledge and capability needed to see to the future of the galaxy.
There will never been a better time to start playing Star Trek Online than during the Delta Recruitment event, which runs from April 2nd to May 21st. Characters made during this time will be Delta Recruits, and they will earn a host of new benefits and rewards to aid them in their leveling experience.
Delta Recruits are specifically designed to rapidly close the gap that exists between new characters and characters that have been in Star Trek Online for years. It’s the most new-player friendly the game has been in almost two years, and the perfect time to join the community of Star Trek Online.
Delta Recruits have a secondary responsibility, and that is to prepare themselves, their crews, and their entire factions for the coming Iconian War. A mysterious benefactor, an experienced captain traveling back in time, will contact all Delta Recruits during their faction’s tutorial and inform them of the opportunities not to be missed during their career. Each faction’s own temporal agency can confirm that what this person said is true, and will guide them using the Delta Recruit window, a new UI element that appears near the Mission Tracker.
Full article here.
This is something never-before-seen in STO. Essentially, in an effort to add to the player base, new players beginning April 2nd can play a parallel story line in addition to the normal story missions at an accelerated XP rate.