What is "Namo Amida Bu". Namo Amida Bu is the Buddha prayer or nembutsu. "Namo" is the little, vulnerable, conditioned self calling out. "Amida Bu" is the Buddha on the Other Shore calling back. Whenever we conceptualise anything, there is always an "other shore", a beyond.
In The Sutra of the Buddha of Immeasurable Life the Buddha says:
"Do not give rise to doubt after my parinirvana. In the future, when the time of the extinction of the sutras comes, out of compassion and pity I will cause this sutra in particular to survive and remain for one hundred years. Sentient beings who encounter this sutra will all, in accord with their aspiration, attain the other shore."