There are several ways in which people pray and seek solace. We all believe that there is one supreme entity which helps us stay calm and listens to our inner voice. Similarly, the followers of Nichiren Buddhism are oft seen chanting the mantra which goes like:
Nam Myōhō Renge Kyō'
If ever you hear it while people pray in group or alone, the vibration and sound does seem to have a soothing effect on the listener as well. Nichiren Buddhism happens to be a branch of of the Mahayana Buddhism which is focussed on the based on what Japanese monk Nichiren taught in the 13th century.
This basically stands for devotion to the Mystic Law of the Lotus Sutra. It believes that everyone is capable of achieving the ultimate enlightenment in the present form and has a Buddha nature residing in each self, which needs to be awakened.
The mantra can be understood in this simpler way:
Namu has been derived from Sanskrit 'namas' referring to 'devotion to'
Myōhō stands for 'supreme law of Buddha'
Myō meaning 'strange', 'mystery' in ancient Chinese
Hō meaning 'law', 'principle', in ancient Chinese
Ren stands for len, 'lotus' in ancient Chinese
Ge stands for meaning 'flower' in ancient Chinese
Kyō meaning 'sutra' in ancient Chinese