The mechanics of it are actually discussed a bit in the upcoming chapter, but I'll just let tell you some details now. FTL can be used on established and charted hyperspace lanes, but it's slower and less safe, think days or even a week to reach your destination depending on how far you're going. A wormhole is instantaneous, which is why the Zetans built one connecting Zeta Prime to Earth, the biggest reason wormholes aren't common around all planets is because they're expensive and difficult to build, think of them like a Suez or Panama Canal tier infrastructure project.

Human Appreciation Societies are Zetans who both regret what they did and a mix of those that just genuinely enjoy Earth culture. They obviously go a little overboard in trying to show humans how nice they are, even among them though the three that follow Jolene around should be considered an extreme case that the rest of the group would probably think is way too far.