That is Short Form is “i.e”
i.e. full form is “That is”. When people want to ask about the That Is means i.e. This short form is derived from the Latin word id est. It is used where we want to restate the idea more clearly or expanding upon it. It means “That is (to say)” in the sense of “that means” and “which means”, or sometimes “in this case”, or “in other words”, “namely”, depending on the context.