the angle between the nearest part of the horizon and a star.
Azimuth describes where around the 360° horizon you can find
the point to look up from. That is azimuth is the angle from the
north point on the horizon to the foot of the vertical circle that
goes through the star. The altitude of the north celestial sphere
here at CSB/SJU is 45°, its azimuth is 0°.
In the below picture what is the azimuth of the red
star (which is on the far side of the celestial sphere)?
Of the yellow star (which is on the near side of the celestial sphere)?