From the manufacturer:
Glimmer Hot Foil Plates add stunning foil features to any project from cards to mixed media and more. The plates are similar to dies but do not have cutting lines or edges. Designed to be used with the Spellbinders Glimmer Hot Foil System (GLS001) and Glimmer foil; each sold separately. Depending on the design, some plates may be used for letterpress and embossing.