Entirely original ideas are rare. Most scholarship in the academic community is influenced in one way or another by the verbal or written ideas of others. What we create during our academic careers -- even in the case of "creative writing" -- is shaped by what we have learned in the past. Originality and creative thinking are important, but in your academic writing you must be sure to place your ideas in the context of the discourse of the discipline. While doing so, you must acknowledge others' ideas carefully by referring to their works within your own writings, using standard procedures that provide readers with enough information to retrieve the source material.
Plagiarism means using another's work without giving credit. Plagiarism can be as blatant as turning in another person's paper or project as your own or buying a paper online, or as sly as simply paraphrasing sections of various works without attributing the source.
One aspect of research is to study what others have published and build on what you have learned. When you quote people -- and even when you summarize or paraphrase information found in books, articles or Web pages -- you must acknowledge the original author. You must put borrowed words in quotation marks and cite your source. You must also provide citations when using others' ideas, even if those ideas are paraphrased in your own words.