Plagiarism is an ethical violation that occurs most often in academic situations when a party takes credits for work that was not of their own authorship VS.
Copyright infringements occur when a party copies, reproduces, distributes, displays or performs, or makes a derivate version of a protected work without permission of the copyright owner or the law.
There are also instances where an act can be both plagiarism and infringement. For example, a student can copy and paste current literature that is not their own work, thereby plagiarizing it, and then publish it online, thereby infringing copyright of the literature.