Er is geen verschil:
E.g. stands for the Latin "exempli gratia" which is translated "For the sake of example; for instance." This abbreviation should be used to provide an example. Here is an example of the use of this phrase: The Libraries collect materials for many subject areas, e.g. Art, English, and Mathematics.
I.e. stands for the Latin phrase "id est," meaning "that is." According to OED, it is used to introduce an explanation of a word or phrase: "that is to say." An example of i.e. would be: The University's Science Library, i.e. Marston, provides materials to support the Mathematics and Physics Departments, among others.
Simpson, J.A and E.S.C. Weiner. "The Oxford English dictionary." 2nd ed. Oxford : Clarendon Press ; New York : Oxford University Press, 1989.