You gain the technological knowledge from the year 2077 Fallout, a world that has been engulfed in nuclear fallout; from advanced laser and plasma weaponry to robotics and clean fusion energy, advanced medicines, deadly viruses, space age alloys, cybernetic implants, teleportation, and much much more. You know everything that has to do with technology seen in Fallout or in any of the canon material. You can also use things from mod content within a certain threshold of lore friendliness (for example, Project Nevada cybernetics would be acceptable, as would official cut content, or things from Van Buren, while a minigun that fires Fat Boy warheads would not.)
As a bonus, you also become a skilled survivor, being able to build things from scraps that you find much easier than a normal person would find, and scavenging for supplies becomes easier for you. Your technology also lasts longer than others surviving even after 100 years and nuclear fallout.