What is the difference between the precession of earth's orbit and the obliquity of earth's orbit?
Obliquity is the constant inclination
The Earth's axis about which we revolve every 24 hours is inclined
to the normal to the Earth's orbital plane (ecliptic), at
nearly. This is called obliquity.
Nodding gently about the center of the Earth, this axis revolves
about this normal, in a period of Great Year = 258 centuries, nearly.
The gentle nodding called nutation is multi-periodic and is
compounded with verily slow revolution about the normal to the
ecliptic called precession.