It is used to express the opposite of, or to contrast with, something that has just been stated. For example: "The job was physically demanding, in contrast to the previous job which had been largely desk-based."

'In contrast' is correct and usable in written English. You can use it to introduce a point or idea that contrasts with a previous point or idea. For example: "John usually eats healthy meals at home. In contrast, he often indulges in junk food when he eats out.".