Question

Explain why this statement is incorrect: "If i find something on the internet, that means it is for the public use,and i can do anything i want with it"

Answer 1

This is Copy Right and it means if you change it enough then you can use it.
For example if you were to use an article on penguins in a video as long as it was not the whole video and you had commentary behind said article that would be fine. 

Answer 2

This would be copyright unless you change it significantly.If you don’t change anything you might be fined.