What Is Duplicate Content and What Is the Punishment For It Today?
Duplicate content refers to the exact same content or writing being in two places online at once. So if you wrote an article and submitted it to one article site and then took the exact same article and submitted elsewhere say to another article site, that would be an example of it.
The entire article does not have to be EXACTLY the same for it to be duplicate content. You can just reuse most of the article and it can still be detected as being a problem. So if for example you try to just change a few words in that article hoping that you would get around this, it would still be considered a problem.
Now that we've established what is duplicate content, let's talk about the more important factor of how it is punished. This isn't necessarily a bad thing. Most article sites, for example, are completely fine with you resubmitting the same content to their site as to somewhere else. Most sites will require that you use the same author or pen name otherwise it just looks like you're stealing outright from someone else.
This is evidence that completely different websites do perform checks on your content which you submit to a certain degree. While this is good because it ensures that no one is stealing your content and resubmitting it to another directory, at the same time it requires that you be aware of this rule and be sure to comply by keeping your pen names consistent between sites.
The one time when the same content is an issue is when the it appears on the same site. In other words it's fine to put the same content into different locations or websites online. Once you put the same content on the same site, say for example you have a post and you post it twice on your blog without changing much to anything, there will be some consequences but never on the level which some make it out to be. De-indexing hardly ever happens and at worst you'll take a hit to your ranking.