Malas
Malas - Prayer Beads
The purpose of the mala from the point of view of the Buddhist, Hindu, Moslem or Christian traditions is for counting of a sacred mantra (prayers) during a period of recitation. For example, one might recite, "Om Mani Padme Hum," the mantra of the Buddha of Compassion and keep a count of each mantra by moving their fingers over each bead. Of course, one can use the mala for any sacred prayer from any spiritual or religious tradition.
In and of themselves wood and stone have a small effect on our physical, emotional and mental nature. If you invest the mala with your aspiration, heartfelt desire to bring benefit to others and devotion, then it will have power equal to your love for other beings. There really isn't any special power separate from your own true Buddha nature to make the mala magical in some way. The power is generated from your own motivation to practice and your mind's ability to connect you with your deepest, truest nature.
Etymology
Mala is Sanskrit, the ancient sacred language of the Vedas, Upanishads, Rig Vedas, and great Buddhist literature roughly means, "Rose" or "Garland." In the Hindu and sometimes certain Buddhist traditions, it is also called a "japamala." In the Mahayana Zen traditions they are also called fozhu and ojuzu, which in other languages expresses roughly the same meaning.