This thread quotes the laws of the
United States of America, and does not apply to users who live in some other country.
In
England, for example, the law is governed by the Copyright Designs and Patents Act 1988:
https://en.wikipedia.org/wiki/Copyright,_Designs_and_Patents_Act_1988
The basic position in England is that it is not a breach of copyright to make a copy of something you already own, for your own sole use. But almost every other type of copying is a breach of copyright.
There are some exemptions for "fair dealing", e.g. if you are copying only a small part of a copyright work. There is a list of examples of what amounts to fair dealing.
Mostly, breach is a
civil matter, meaning you might be sued for the breach and have to pay compensation (to the copyright owner). This means, in effect, that you are not likely to be sued unless you are doing something that warrants the time and expense of a lawsuit.
But selling a copy, or making a copy available to the public, is a
criminal offence. There are other criminal offences under the Act too. This means the copyright owner is relieved of the cost and hassle, which falls instead on the police or another public body, so the owner is more likely to take action in the case of even a less serious breach.