our answer to this, if you're curious, is that they mean the same thing, but calling it a bug has implications that it's less significant, and calling it a glitch implies that it's more significant
In the context of video games, "the life counter doesn't render correctly for a few frames after you get a 1-up" would be a bug, and "the HUD disappears and doesn't return until you reboot the game if you get a bonus time pickup on the same frame the timer runs out" would be a glitch
-F