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question I'm confused. Why do people say "Senpai" or "Sama" or "Kun" or "Chan" or those other stuff like that arrow 3nodding

those are honorifics attatched to peoples names. Lets put this into context to help it stick:

Lets say you have a Japanese friend, Tanaka Ichiro. You are not very close to him so you will call him by his last name, Tanaka.

Sempai: You are a highshcool freshman, he is a senior. You would address him as Tanaka-SEMPAI. Or in reverse, if YOU were the senior and he was the freshman you could call him Tanaka-KOHAI (and he would call you sempai)

Sama: Used for someone who is of higher status than you. So say that he is your boss, you would call him Tanaka-sama.

Kun: Tanaka Ichiro is your classmate. Same age and grade. He sits across from you and you don't know him too well, so you call him Tanaka-kun. However, say you grew up together and he sits right next to you. You would call him Ichiro-kun, since you are close to him. So Kun is used for people, almost always boys (but women are sometimes addressed as -kun too, in places such as the office), that are of your status.

chan: Tanaka Ichiro is the 5 year old across the street. Because he is young, you address him as Ichiro-chan. Chan is used for little kids, the feminine equivalent of -Kun, or a boyfriend. So let's say Ichiro is now Kumiko, your best friend. You could call her Kumiko-chan. Or, Ichiro is your boyfriend. You could call him Ichiro-kun, or Ichiro-chan to be cute.

Get it? Learning is always best in context.

Note: Since you are asking about honorifics I am going to assume you are a beginner. If you notice, I alternate by calling him Tanaka and Ichiro. Names are always "LAST NAME-FIRST NAME", the reverse of English. So you ONLY call someone by their first name if they are close to you or family. It could be rather rude to call your older classmate by their first name. It could get you fired if you call your boss "Ichiro-kun". To clear up any confusion, you should look up honorifics and ways to address people just in case.