It is quite difficult to translate...
The meaning is "Erasing is like not seeing (anything)".
You have to use imperfetto when the action happens in the past.
Marco ieri scriveva una lettera.
Yesterday Marco wrote a letter.
It could be used also like the english "used to":
Quando avevo 8 anni, giocavo con i miei amici.
When I was 8, I used to play with my friends.