Personification is assigning human attributes to an animal or non-human object. Death, for example, is personified as a woman below:
Her lips were red, her looks were free,
Her locks were yellow as gold:
Her skin was as white as leprosy,
The Night-mare LIFE-IN-DEATH was she,
Who thicks man's blood with cold.
'The game is done! I've won! I've won!'
Quoth she, and whistles thrice.
The Mariner calls her life-in death, but in fact, she is death, for she takes 200 lives ("Four times fifty living men"). She is described as looking like a living woman, though with very white skin, and she uses the triumphal language of a person who has won a game of chance.
The albatross is also personified, as it is described with human imagery:
As if it had been a Christian soul
The sun is also personified, described as "he" rather than "it" in the following:
The Sun came up upon the left,
Out of the sea came he!
The above imagery positions the sun as something of a person rising out of the sea.
A paradox is a statement that seem self-contradictory or absurd. Imagery is description that uses any of the five senses of sight, sound, taste, touch, and smell. The most famous paradoxical image in the poem is "water, water everywhere and not a drop to drink."
It is also paradoxical to call the personified death above "life-in-death" and to describe her as both red-lipped and yellow haired and white like leprosy. This suggests, paradoxically, that it is the red and yellow sun bringing death, a seeming contradiction as we usually associate sun with life-giving force.
The corpses, paradoxically, don't decompose or smell bad: "Nor rot nor reek did they." (This foreshadows that they are not really dead.)
The personification reinforces the idea that all of nature is alive with a divine life force and should be treated with respect. The paradoxical imagery underscores the supernatural strangeness of the Mariner's experience.