The earth from how we normally view it on maps, with the North pole on top and the South Pole on bottom has a polar axis that cuts from to bottom. (From the inside)

The top of that Polar Axis, where the North Pole is, is called the North Celestial Pole. The bottom of the Polar Axis where the South Pole is, is called the South Celestial Pole. Cutting through the middle of the Polar Axis, is the Celestial Equator.  Laying almost on top of the Polar Axis, the Celestial Meridian is a line that follows the outside of the globe going from the top and bottoms points. (North Celestial to South Celestial.)

Based on the Sun's position in the sky, the earth's polar axis sits at a 23.5 degree inclination. This means that our Celestial Poles are not the same positions as the "top" and "bottom" of the sun's poles. Our Celestial meridian and equator are also not the same angles.

The top of the sun is the Zenith. Making this the top of the earth when it is viewed at inclination.  The bottom of the sun is the Nadir. Making this the bottom of the earth when viewed at inclination. The middle cross section of the sun is the Horizon, making this this the cross section of the earth when viewed at inclination.