i.e. | e.g. | re

• i.e.: When you mean "that is," use "i.e." It is an abbreviation for the Latin phrase id est
• e.g.: when you mean "for example," use e.g. It is an abbreviation for the Latin phrase exempli gratia.
• re: a prefix, occurring originally in loanwords from Latin, used with the meaning "again" or "again and again" to indicate repetition, or with the meaning "back" or "backward" to indicate withdrawal or backward motion. In contemporary 'email language', it means "about" or "in reference to".