Amulets, charms. The practice of obtaining amulets from shrines and Buddhist temples is almost universal in Japan. O-mamori are traditionally small brightly coloured brocade bags with drawstrings, usually with an inscription giving the name of the shrine and perhaps the benefit (riyaku) for which the amulet has been obtained. Recently, innovative o-mamori including those shaped like (or doubling as) decorative telephone cards have been introduced. O-mamori are acquired by children (see Shugaku ryoko), by people who are sick, at New Year, for passing an examination, for traffic safety (kotsu anzen) and at the time of a pilgrimage or occasional shrine visit. Mamori means 'protection' so strictly speaking the function of an amulet is to protect against bad influences, disaster etc. while a talisman (o-fuda) is supposed to attract or channel good fortune, but good fortune is the absence of bad so there is considerable overlap in the function of o-mamori and o-fuda.
A Popular Dictionary of Shinto. Brian Bocking.