So think of copyright infringement as using someone else’s copyrighted work without their permission – for example, you make a video and post it on your YouTube channel and you’ve used a popular current song as the soundtrack but you didn’t get permission from the label to use that song. Or you post a series of photographs on your ad-sponsored travel blog that are not licensed for commercial use and you didn’t get permission from the photographers to use them. Even if you have captions giving credit to the photographers and citing your sources – which is attribution, which is good - it doesn’t mean you have the photographers’ permission to use their work, which could be infringement, especially if your use doesn’t hold up as a fair one.
Now let’s say you’re posting those same copyrighted images without permission AND passing them off as your own work WITHOUT giving credit to the photographers - now you’re plagiarizing in addition to infringing on copyright. Or let’s say you’re writing an essay and you copy a few sentences from a reference book word for word and you don’t cite the source – that’s also plagiarism. It may not be considered illegal infringement because the amount copied is fairly inconsequential, but it’s still plagiarism and it's still unethical.