In the Christian tradition, holy cards or prayer cards are small, devotional pictures for the use of the faithful that usually depict a religious scene or a saint in an image about the size of a playing card. The reverse typically contains a prayer, some of which promise an indulgence for its recitation.
The circulation of these cards is an important part of the visual folk culture of Roman Catholics, and in modern times, prayer cards have also become popular among Orthodox Christians and Protestant Christians, although with the latter, biblical themes are emphasized within them.[1][2]
Protestant prayer cards tended to emphasize biblical themes as opposed to devotional subjects (Leonard Primiano, personal communication, 2011).
In recent years, holy cards have become increasingly popular among Orthodox Christians as well.