Plagiarism involves using others' words or ideas and presenting them as one's own without proper acknowledgement. It can be deliberate cheating or accidental failure to cite sources. Common forms of plagiarism include copying text from sources verbatim or with minimal changes, paraphrasing others' ideas without citation, or overly relying on direct quotations. To avoid plagiarism, one must understand what constitutes plagiarism, plan original work, learn how to properly cite sources, and use quotations and notes correctly when incorporating outside information and ideas.