ligatures are when you join two or more glyphs into a single one. For instance, instead of having the two characters = and > to form => if you had ligature support you would see ⇒. Some terminals have support to recognize sequences like => (and others obviously) and turn them into their corresponding ligatures (only for display though, the actual file contents remain umchanged)
There was also a plan to explode nuclear bombs on shorelines to create artificial harbors, and of course the infamous Project Orion, a manned interstellar spaceship powered by exploding hydrogen bombs. Doing unhinged shit with nukes was all the rage back then I guess