What are the rules with copy right?

[Jackson Molloy]

I was wondering what are the rules concerning copy right. Here is an example (copy and paste the following in youtube for the video i will reference):
Eminem Berzerk, Nicki Minaj Sex Tape? DMX Naked
This video has both music and videos that are not there own creations but the channel still has ads and still makes money i'm assuming. Are there not some laws against this?

If i was to use others music or video in music in my own productions would i have any problems?

 

[Gabriel]

The video may be monetized by the copyright holder.

 

[Wreckless Eating]

 

[Jackson Molloy]

Thank you Gabriel and Wreckless Eating!So with the fair use rules I could add any content to a video as long as the purpose is to comment on the content?

 

[Mark Robinson]

.

 

[Jackson Molloy]

GREAT! Cheers i think i understand everything now