Someone puts it there. Sometimes it's the legal rightsholder (or someone the rightsholder has authorized), but often it isn't.
If it is copyrighted content, yes.
Yes, just make sure to add the audio to your video in a video editor and then upload your finished content onto YouTube. Also make sure that there is no copyrighted background music or any copyrighted content in the background.
Both kinds of information appear on the web, although copyrighted content is more common.
It definitely is NOT. Many companies post images, logos, and stories that are copyrighted. MOST government websites have content that is not copyrighted, some will have content that IS copyrighted, and used with permission of the owner. When reading an article, or viewing images, scroll down- you may see a notice that says something like "All rights reserved" and the c in a circle symbol that means copyrighted- and a date. That is NOT public domain.
Regretably, no, as they are copyrighted content.
You would need to gain permission to use copyrighted content if you are going to make money from it. Generally, you can use copyrighted content (covering songs and such) if you make no money from it. The copyright holders might put adverts on your video so that they make money from it instead.
Anything which is copyrighted.
It is still copyrighted. There's no exception for things that are out of print or unavailable.
There is no magic number for the amount of copyrighted content used that will lead to a copyright notification. Fair use is a very ambiguous rule and is judged on a case-by-case basis. To be safe, avoid using any copyrighted content in your videos at all.
cant theyre copyrighted
If it does not contains any copyrighted content, such as BIOS/Firmware, yes.
Yes And No! Users Can Report that and the Supervisors or other members can remove the hole post. As long as the member uses this text it is not Copyrighted.