I.E. means “that is”.
Like many phrases in English, i.e. is borrowed from Latin. I.e. stands for ‘id est’, which roughly translates into “that is.”
I.e. is often used to indicate an alternative phrase. It can be used to explain, clarify or rephrase a statement. Depending on the structure of the sentence, i.e. can be used instead of “that means”, “which means”, “in other words”, or sometimes “in this case”. In America English, i.e. is followed by a comma, whereas in UK English there is no need for a comma.
I like to shop at the supermarket, i.e. (that is) I like their range of products.
Often, i.e. is confused with e.g. which means ‘for example’.