In this example, the writer has just copied text from a scholarly article and tried to pass it off as their own work. There are no citations, and the writer uses the complete text without even trying to paraphrase. This is incorrect and counts as plagiarism.
In this example, the writer has completely copied the original article, but has tried to attribute the information. There are a number of problems here. First, the person has copied too much of the original text. Also, the text was not cited correctly. This is also incorrect and counts as plagiarism.
In this example, the author has taken an idea from the original article and put it in their own words. The problem here is that the author did not give credit to the original writer for his idea. This is incorrect and counts as plagiarism.
In this example, the author has quoted the original text, but has failed to give credit in a way that let's the reader follow the citation back to the original author. Here, for example, the author has only cited the database where they found the information, not the author himself. This is incorrect and still counts as plagiarism.
In this example, the author has used both a quote AND paraphrased a section of the original article. The author has then cited each correctly in parenthetical citations AND cited it in their references section. This is in APA citation style, there are other ways to cite information correctly in other styles like MLA and Chicago. This is correct and is NOT plagiarism.