Namo Amitabha is a chanting/prayers. Namo means converting （归依） , Ami means infinity, Tabha means the Buddha.

OM MANI PADME HUM /k/ please calm down.

In case /k/ don't know the meaning of OM MANI PADME HUM,

OM represents the body of all Buddhas, it also begins nearly all mantras, purifies the veils of body;
MANI means "jewel" in Sanskrit, purifies the veils of speech and mind;
PAD ME, means "lotus", purifies the veils of conflicting emotions;
HUM represents the mind of all Buddhas and often ends mantras, purifies the veil that covers knowledge.