What is positive contrast? What is contrast?

Set-off refers to the use of similar or opposite conditions between things, using some things as a set-off to highlight what is to be expressed. It can make the things that are set off more prominent and vivid. There are two types of foil: positive and negative. Using similar conditions of things to set off is positive contrast; To set off with the opposite conditions of things is to contrast. It emphasizes "lining" one by comparison. For example, Cui Hu's titled "Village in the South of the City": "Last year today, at this gate, peach blossoms set each other off. People don't know where to go, and peach blossoms are still smiling in the spring breeze. " This is a lyric poem. In the seemingly narrative, by comparing last year's today with this year's today, the author highlights the sentimental feeling that this year's peach blossom is "still" and the face is no longer at this moment. The key point here is to set off (contrast) this year's loneliness, sadness and helplessness by comparing with last year's joy!