Rudraksha beads are the seeds from a number of Elaeocarpus trees, which have their origin in ancient Vedic legend - "Lord Shiva was meditating on how to relieve the troubles of the world, while doing so warm tears of compassion fell from his eyes. These tears upon reaching the ground became the Rudraksha trees. Since then, the devotees of lord Shiva have used these sacred beads for japa and meditation.” - Shiva Purana
Mantra yoga, often called "mantra meditation", is part of the nada school of yoga, an ancient system of yoga which focuses on sound vibrations and their use as a means of meditation, healing and influencing the external world. Especially in the form of mantras, which are formulaic sound vibrations that contain sacred syllables representative of and containing spiritual power.
Mantras are formulaic sound vibrations that contain within them sacred syllables representative of, and containing, spiritual power. Reciting mantras in certain ways and meditating on them allows you to focus the spiritual power innate in the mantra.