A restatement of the original passage in your own words.
The length of the paraphrase is usually as long as the original. In this respect, it is different from a summary.
Usually, only sentences or paragraphs are paraphrased.
Example of a Paraphrase (taken from the Purdue University Online Writing Lab. http://owl.english.purdue.edu/handouts/research/r_quotprsum.html)
The original passage:
Students frequently overuse direct quotation in taking notes, and as a result they overuse quotations in the final [research] paper. Probably only about 10% of your final manuscript should appear as directly quoted matter. Therefore, you should strive to limit the amount of exact transcribing of source materials while taking notes. Lester, James D. Writing Research Papers. 2nd ed. (1976): 46-47.
A legitimate paraphrase:
In research papers students often quote excessively, failing to keep quoted material down to a desirable level. Since the problem usually originates during note taking, it is essential to minimize the material recorded verbatim (Lester 46-47).
THE ONLY WAY TO AVOID THE BIG “P”!
For both paraphrasing and summarizing, it is imperative that you understand completely the material. It may take 2 or 3 readings to reach the point where you can restate in your own words what was meant in the original source.