Declination.

Declination is measured in degrees.
It is measured from the celestial equator.

The declination of the Sun is the number of degrees the Sun is above, or below the Celestial equator.

Solstice and equinox at midday as the sun crosses the meridian.

The angle of the Celestial equator from the zenith (zenith angle) or from the ground up (elevation angle) is determined by the angle of the Pole.

When you know your latitude, you can work out the angle of the equator.

Northern hemisphere.
Same in south, just no Pole star!

The declination of the ecliptic changes as the earth rotates.
Looking south at midday, at the summer solstice - the ecliptic is at its maximum angular height above the equator. Again looking south, at midnight - the sun is at its maximum angular distance below the equator at midnight.

At the winter solstice the positions are reversed. The ecliptic at midday is at its maximum angle below the equator at midday, and at its maximum angle above it at midnight.

The declination of the ecliptic at the equinox follows the same rule; again looking south - at the Vernal equinox, the ecliptic is at its maximum declination below the equator at 6 AM and at its maximum at 6 PM.

Reverse that in the autumn and the ecliptic is at its maximum declination at 6 AM, and minimum at 6 PM in autumn.
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This yearly cycle is repeated every day.

One rotation of the earth takes on average 23 hours, 56 minutes. One rotation using the sun rather than the stars as a marker takes 24 hours. But the earth is moving around the sun (this accounts for the time difference). Therefore the position of the highest angle of the ecliptic slips backwards relative to the sun, by 4 minuets (time) a day (which works out as 1 degree -angle - per day.).