lǎo / shī / yòng / léi / shè / bǐ / zhǐ / zhe / hēi / bǎn / shàng / de / zhòng / diǎn / nèi / róng / jiǎng / jiě

老师用雷射笔指着黑板上的重点内容讲解。

The teacher uses a laser pointer to point to the key content on the blackboard for explanation.