An idiom meaning a huge, incomparable difference—literally 'the difference between clouds and mud.'
プロの演技と初心者の演技では雲泥の差がある。
There is a world of difference between a professional's performance and a beginner's.
値段と品質に雲泥の差がある商品もある。
Some products show a huge gap between price and quality.
説明と実際のサービスは雲泥の差だった。
There was a vast difference between the description and the actual service.