ТО ЕСТЬ

that is, i.e., that is to say, in other words

1. that is to say

(как поправка, уточнение) I (you, etc. ) mean

~ вы ошиблись you mean, you made a mistake

2. (выражает удивление) what do you mean?

~, как - не знаешь? what do you mean, you don`t know?