I have a small confusion about one "Hadeeth" I didn't know exact "Hadeeth" but I know the meaning. (The "Hadeeth" reported from "Bukhaari" Via Abu Hurayrah, may Allaah be pleased with him, from Prophet, sallallaahu alayhi wa sallam, I got two type of knowledge from Prophet, sallallaahu alayhi wa sallam, one is I am explained to all people, but another one if people here they are cut my neck).
I need the authenticity of this "Hadeeth" if this Hadeeth is "Saheeh" I need the explanation and original meaning. This is very urgent.

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.

You probably mean the narration reported by Abu Hurayrah who said: "I have memorized two kinds of knowledge from the Prophet . I have propagated one of them to you but if I propagate the second to you, then my pharynx (throat) would be cut (i.e. I will be killed)." [Al-Bukhari] This narration is authentic as it is reported by Imaam Al-Bukhari as the narrations compiled by him are the most authentic books. Therefore, he learnt two kinds of knowledge:

-         The first kind of knowledge: this is the narrations that he spread among the people, and these are the narrations about what is lawful and unlawful, the recommended acts and other knowledge on rulings and moral conducts.

-         The second kind of knowledge: Ibn Hajar said that the scholars are of the view that this knowledge is about the narrations in which the names of evil rulers, their condition, and their time is mentioned. So Abu Hurayrah did not reveal it openly but used to give hints about it as he was afraid of them. For instance, he said: 'I seek refuge in Allaah from the beginning of the sixties (i.e. the sixtieth year A.H.) and from the rule of young people.' This is a hint to the reign of Yazeed Ibn Mu'aawiyah who was young. This reign was in 60 A.H. and Allaah responded the supplication of Abu Hurayrah as he died one year before this time.  

Allaah Knows best.