Plagiarism is stealing of the text without giving credit to the source.
Some type of common plagiarism:
Complete Plagiarism: As in the case of Alan, who submitted a paper written by someone else without any citing or crediting the source.
Misleading Citation: When someone use different types of resources and mistakenly cite wrong source. It comes in Misleading Citation or Source base Citation.
Paraphrasing plagiarism: Means using someone else work and making some minor changes and crediting as own work.
Accidental plagiarism: When citation style or format gets wrong.