The cover or pages become stained, causing what was white to become tanned or browned.  The paper of the comic in the front of the photo is clearly darker than that of the comic in the back.

Portions or all of the cover becomes faded or discolored when a book has been exposed to sunlight or other elements.  The upper right hand corner of this comic shows such discoloration.

Damage that pushes in a  corner, usually resulting from direct impact if a book is dropped on a hard surface.  You can see such a dent in the corner of this comic.

A fold that damages the color, leaving a permanent line.  The diagonal line in the upper right hand corner of the photo shows a color breaking crease.

Permanent folds that do not result in color damage.  The lines in the upper right corner of the photo show examples of folds.

When moisture causes fungal damage to the comic.  Usually seen when comics are stored in damp basements.  The dark spot between the "L" and "K" of the word Hulk is an example of mold. 

Pieces of the comic are missing from damage or accumulated wear.  This can be anything from a small chunk up to the entire cover. This comic shows many missing pieces on the edge.

When the sharpness of a corner is blunted from repeated wear.  The upper and lower corners of the comic in the photo are examples of rounding.

Stains that cause discoloration of the comic.  As in the photo, this is generally easier to see with a white background.

The cover rolls towards the front of the comic if stored improperly, so that the staples face forward.  As in the photo, this may also cause the cover to display at an upward or downward angle.

Creases or other damage that occurs along the spine.  All of the little white horizontal lines along the spine of this comic are an example of spine wear.

Home repairs for tears or loose pages, using scotch tape.  Look along the right side of the comic in the photo and you can see the yellowed strip of scotch tape.

Exposure to water or other liquid that causes discoloration and/or "waviness" to the comic.  This is visible in the vertical lines/shadows of the photo.

Permanent damage caused from markers, pens, crayons, etc..  This photo shows damage from writing with pen, as well as typewriter correction fluid in the "ch" of the word Schwinn.