When you erase something, you eliminate or delete it, often by physically wiping it out. It's easy to erase chalk from a blackboard, but not so easy to erase graffiti from the side of a building.
There are several ways to erase: you can erase a pencil mark with an eraser; you can digitally erase information on your computer or recording device; and you can figuratively erase something by removing all evidence of it. Peaceful people hope to erase war from the earth, for example — to take away every last trace of it. The Latin root eradere means "scrape out."