The cornea is the front, clear surface of the eye. An abrasion is another word for scratch or scrape. Scratches to the cornea typically occur from sharp objects coming into contact with the eye, such as fingernails, tree branches, or rubbing the eye when something is stuck inside (foreign body). Another common way is projectile or flying particles such as metal or dust getting into the eye. Other than pain, individuals may experience red eyes, blurry vision, light sensitivity, excessive tearing of the eye, and a feeling that there is something stuck in the eye (foreign body sensation).
Here is a video that presents a corneal abrasion overview.
Treatment of a corneal abrasion depends on how severe it is. Some may resolve without any treatment or just require artificial tears. Larger abrasions may require an antibiotic drop to prevent an infection from occurring in the scrape. Drops that dilate the pupil may help with the pain (although will cause temporary blurring of the vision in that eye). Bandage contact lenses are sometimes also used.
The following video presents treatment options for corneal abrasions.