Information that can be dangerous to know about. Some examples are how locking your knees too hard can cut off circulation and be lethal, or how grabbing your thumb and shaking your wrist can break an important part of your thumb. Yes, obviously there are much more dangerous things to know about, but that's up to you I guess.
Totally real person 1: Have you heard that grabbing your thumbs and shaking your wrists can break your thumb?
Totally real person 2: That's an infohazard
While our lifespan is the number of years we will live, our healthspan is the number of healthy years we will have and our sexspan is is the number of years we will continue to be healthy enough to continue having an active sex life.
A lighthearted reaction upon receiving disappointing news of some sort. Usually something that isn't a particularly a big deal, esp. when it primarily affects someone else - sort of a mild schadenfreude. Sometimes doubled or tripled, and possibly said in a sing-songy voice for added comedic effect to imitate a muted trumpet, which is how the meme originated.