Shiva ratri means night of Shiva. We can ask Shiva for blessings to help us progress spiritually on the path of devotional service and destroy our material ego based on this temporary body and mind.
The most famous Shiva mantra is probably ‘Om namah Shivaya’. In this mantra respect is shown to Shiva, that malevolent deity of destruction. Literally ‘Shiva’ means auspicious, auspicious and friendly. ‘Namah’ means paying respect, bowing down and worshipping. ‘Om’ is a cosmic and auspicious syllable that is recited at the beginning of many mantras.
In South Asia Shiva Ratri is celebrated on March 8th.