What Are Focal Headaches?

i was diagnosed with trigeminal neuralgia from my GP ive been off work for six months with the worst pains in my head ive ever experienced ive seen a neurologist who gave me a cat scan and recieved a letter with a diagnosis of Focal Headaches im taking 900mg of carbamazipine that has just got me to a level or normality but with zombie like side affects what are Focal headaches