My problem was to translate from PT to EN. I answered "He can put it in that corner" only to be told it should be "He can put this in that corner". I know that is the literal answer but I think Duolingo was a bit mean.
I think it's the difference between an interior corner (canto) and an exterior corner (esquina). So you can sit in the "canto" of the room, but you meet your friend on the "esquina" of two streets. There may be some crossovers of the meanings which escape me though.
By the way, I can't remember Esquina being used for anything besides street corners.