This is the bija of Narasimha, a very fierce half man half lion incarnation of Lord Vishnu. Ksha is Narasimha, ra is Brahma, au means with teeth pointing upwards, and bindu means dispeller of sorrow.
The science of Mantra is very complex. There are even Mantras for such specific purposes as curing snake bite and chronic disease, but these are of a lower order. In the modern world, the power of gross sound vibration is just beginning to be utilized in physical therapy, and its potential is being tapped in other fields. The ancient Indian sages had this sophistication thousands of years ago. They have used sound in its gross and subtle states to penetrate the planes of human consciousness and to reach the divine vibration that is the experience of God. Beginning in OM and dissolving in OM, the Mantra comes full cycle.