Erasure is the act of erasing, deleting, or removing something. It's tricky to write an essay on a typewriter instead of a computer, because it's hard to hide any erasures.
An erasure can be made, appropriately, by erasing pencilled words with an eraser, but there are many other kinds of erasure. You can experience an accidental erasure of a whole day's work by hitting the wrong button on your laptop, and you can choose to hide details of your past with the kind of erasure that involves leaving certain information out when you tell your story. The Latin root is eradere, "scrape off" or "remove."