Japa — from the Sanskrit jap, “to mutter” — is the repetition of a divine name. A mala of 108 beads is the traditional counter. The forms include spoken (vaikhari), whispered (upamshu), and silent mental (manasika) — the last considered the most powerful.
The promise across traditions that practice it: eventually the repetition becomes self-sustaining. One stops doing it and finds it still there.