The meridian and the equator.

Celestial North Pole
The 'poles' of the Earth both have a latitude of 90 degrees.
There is a north and south pole.
The region of space above them is known as the Celestial Pole.

Celestial North Pole
The Celestial Equator is 90 degrees to the Celestial poles. The latitude at the equator is 0 degrees.