詫び: tranquil simplicity from natural colours and forms, from natural materials such as wood, bamboo, earthenware. Human attempts to draw out the distinctive beauty of these materials. No decoration or showiness. Difficulty: Line between beauty and shabbiness.
さび: means rust or patina of age; beauty of passage of time. Abuse of daily use, and lovingly repaired, and impermanent. Reminds us of the cycle of life.
すき: subtle elegance + delight in the unusual. Originally, it meant heretical beauty. Around 1500, the aristocracy was also looking for new, original things, trying to impress each other with their free taste, possibly leading to the rise of 詫び. See the story about the 山ノ井
茶入 described in CQ78.
➡️ All this needs to be natural, though, without striving