The use of mala is primarily for spiritual and chanting purpose. Many use beads mala as ornaments. And also more used for counting while doing chanting.
Usage of mala / rosary
These are used for keeping correct counting while chanting. While we chant, we generally recite some common word ( called Mantra ) for certain number of times. That means while repeating the mantra or name of god, we use the beads of the mala for counting purpose. This is a ancient practice in India and known as Japa.
There are different ways of using the beads mala for counting. There are certain rules to be followed in certain counting / japa practice. The way we hold the mala while chanting is the rule. Generally we avoid touching the beads with index finger. There is a center bead in a beads mala called sumeru. We start counting from sumeru and then roll each bead as we count, then we stop when we again reach the sumeru. The rule is - Never pass over the sumeru bead.
When someone does more japam then he simply turns round the japa mala and then again does the counting backward. The touching with index finger or the ego finger is always avoided.