Copyright is a law which gives content creators exclusive rights to their own work. this law is automatic as to not make the process troublesome
after enough time has passed a work will go into the public domain, which gives everyone access to it for free. anything not copyrighted is in the public domain automatically
if you want to use something copyrighted you need to first as the creator. so if you want to use someone's book to publish a news article. the same thing goes for photos and pictures. and never forget to give the creator credit by citing your work
however, should you use someone else's work for education or research. you need not ask permission as it is fair use.
Just because you buy the work, does not allow you to reproduce or copy it.