Xiehouyu is a special type of Chinese expression that uses four or fewer characters to create a very vivid image in our minds.
Imagine you eating so much candy that you feel sick, and then your mom tells you "I told you so". In Chinese, your mom might say "吃饱糖腹泻" (chi bao tang fu xie) which means "eating too much candy makes your stomach hurt", and has a rhyme to it which makes it more memorable.
Xiehouyu can also use a play on words, where the characters sound similar but have different meanings. For example, "黄袍加身" (huang pao jia shen) means "wearing a yellow robe", but it also sounds like "皇帝加身" which means "become the emperor". This phrase is often used to describe someone being promoted to a higher position.
Overall, xiehouyu is a fun way to express yourself and create vivid images or play with words. It's kind of like a puzzle or game where you try to find the perfect combination of characters to create a memorable phrase.