"Prayer Flags are inscribed with auspicious symbols, invocations, prayers, and mantras. Tibetan Buddhists for centuries have planted these flags outside their homes and places of spiritual practice for the wind to carry the beneficent vibrations across the countryside. Prayer flags are said to bring happiness, long life and prosperity to the flag planter and those in the vicinity. Dharma prints bear traditional Buddhist symbols, protectors and enlightened beings. As the Buddhist spiritual approach is non-theistic, the elements of Tantric iconography do not stand for external beings, but represent aspects of enlightened mind i.e. compassion, perfect action, fearlessness, etc. Displayed with respect, Dharma prints impart a feeling of harmony and bring to mind the precious teachings."
taken from prayerflags.com