Complex sentence: Unlike ostension, which is the "act" of showing a sample, or defining its label, exemplification is "possession" of a property plus "reference" to its label (Goodman, 1976).
Split into simpler sentences: Unlike ostension, which is the "act" of showing a sample, or defining its label, exemplification is "possession" of a property plus "reference" to its label. Basically, possession of a property amounts to "being referred to" by its label (Goodman, 1976).