Example 1:
According to Piper (2003), "God is the one Being in all the universe for whom seeking His own praise is
the ultimately loving act" (p. 49).
This is NOT plagiarism. Quotation marks are properly placed around the author's words and the date and page number of the source is given.
Example 2:
According to Piper, God is the one Being in all the universe for whom seeking His own praise is
the ultimately loving act.
This IS plagiarism. There are no quotations placed around the author's words, and no information about the book is given.
Another example:
James K. Polk was the 11th President of the United States.
This is NOT plagiarism. Many experts agree that if the fact you're citing can be found in five independent sources, it's considered "common knowledge" and you're not required to cite it in your paper. The above example would fall into that category.
Plagiarism: What It Is and How to Recognize and Avoid It, created by Indiana University