i.e. is a Latin abbreviation for id est meaning "that is." This would be used when the intent is to clarify or explain the previous statement. For example, the federal government's highest judicial body, i.e., the Supreme Court. Or, his children (i.e., Matthew, Mark, Luke, and Joan). It should not be confused with the Latin abbreviation e.g. would be used when the intent is to simply provide an example.
[Last updated in April of 2022 by the Wex Definitions Team]