When the content of any given material, be it an article, a review or a paper, is checked, similarities to other such materials may appear. This does not, however, automatically mean that the respective content has been plagiarized. At this point this simply means that similar content to other such materials has been found but it does not imply dishonest or illegal practices.
Especially in academic papers, a high percentage of instances of similarity can easily be explained through comparison and an analysis of the content and its context. Quoting the title of another paper will be detected as a similarity. So will names, book titles or bibliographies, references and quotes, common phrases and constructs, etc. Though similar, they do not qualify as plagiarism because plagiarism implies using someone else’s work or ideas as if they were one’s own.