system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What does it mean to say the earth is tilted on its axis? Tilted with respect to what?
gpt
>ELI5: What does it mean to say the earth is tilted on its axis? Tilted with respect to what?  
  
Tilted with respect to the ecliptic, the plane defined by the Earth's orbit around the sun.  

You can grab a pen and draw a circle on a piece of paper. That pen could be held perpendicular to paper while you're tracing the circle or you could hold it at an angle - *tilted* relative to the plane of the paper.