It's important for you to understand that plagiarism isn't always intentional, but that doesn't mean it's ever okay. Here's a quick definition of plagiarism: "Using another person's words or ideas without giving credit, either by accident or with intent."
Even though plagiarism can happen by accident, that doesn't mean you won't face academic consequences. One of the best ways you can work to actively avoid plagiarizing is by being vigilant about citing your sources.
Watch the video below for a great explanation of plagiarism: