When you plagiarize, just as when you cheat on an exam, you treat unfairly those who play by the rules. You seek an unfair advantage over them, and inevitably, you will find yourself looking down on those who devote their time and energy to the task which you have cheated on. Third, when you use other people's words and ideas without their permission, it is stealing . It would be wrong to sneak into a factory and steal the products manufactured there during the day, and in the academy, words, ideas, paintings, compositions, sculpture, inventions, and other creations are what we produce. It is wrong to steal them and claim them as your own.
Plagiarism is a big deal in the academy.
There are many forms of plagiarism, some less flagrant than the examples I began with. However, you need to understand and avoid all forms of plagiarism. Some forms of plagiarism are probably not obvious to you, so I want to spell them out in detail. I think much plagiarism is inadvertent and unknowing. I want to help you avoid that potential embarrassment.