An idiom meaning a tremendously large difference between two things; a world of difference.
新人の頃と今とでは、仕事のスピードに天と地の差がある。
There is a world of difference in work speed between when I was a newbie and now.
この二つのカメラは画質が天と地の差だ。
The image quality of these two cameras is poles apart.
彼の昔の成績と現在の成績は天と地の差で、努力の成果が出ている。
His past grades and current grades show a world of difference; his effort has paid off.