This is a four-character idiom (成语) meaning 'weightier than Mount Tai' — used to describe something of the utmost importance or significance. Mount Tai, a famous mountain in Shandong, symbolizes stability and weight in Chinese culture. You'll often hear it paired with its opposite, 轻于鸿毛 (lighter than a swan's feather), as in 人固有一死，或重于泰山，或轻于鸿毛. Note: the character 重 here should be read zhòng, not chóng, but the row's pinyin is given as 'chóng' — a likely data error.