Mantras are the accumulation of words, from which one can achieve adored and destroy negative obstacles. In the word Mantra, 'Man' means mind and contemplation and 'Tra' means power and protection.
On the next level Mantra, that is, by contemplation of which man gets the knowledge of his uniformity from the whole universe. At this stage, contemplation also stops, the mind becomes relaxed and the mantra also becomes calm. In this situation the person is freed from the cycle of birth and death.
There are many benefits of chanting mantras, e.g. Spiritual progress, destruction of enemy, attaining supernatural power, destruction of sin and purification of words.
There is a difference between chanting mantras and chanting the name of God. Many rules have to be followed to chant a mantra but it is not required to chant the name of God. For example, chanting mantras is necessary in a positive atmosphere; but chanting the name of God can be done anywhere and at any time.
The spiritual energy produced by chanting the mantra can be used for good or bad work. It is like earning money, how to use the money depends on the person who earns the money.