used especially in writing before a piece of information that makes the meaning of something clearer or shows its true meaning

The hotel is closed during low season, i.e. from October to March. 这家旅馆在淡季，即从10月到3月，关门停业。

The price must be more realistic, i.e. lower. 价格必须更切合实际些，也就是说要更低些。