Paraphrasing is taking a small excerpt from your source and putting it into your own words, whereas summarizing gives an overview of the main points from an entire source (e.g., and entire book or article). In both cases, it is important to cite your sources.
Here is an example showing quoting, paraphrasing and summarizing in the same short paper sample:
Since the early 20th Century, the public and experts have debated whether vaccines are effective, how they should be regulated and, more recently, whether vaccines cause Autism (Matlesky 32). Of all the questions surrounding vaccines, however, none is more passionately argued than mandatory vaccination programs for children attending public schools. In a key 1922 case, Zucht v. King, the Supreme Court upheld states’ right to require vaccinations for children attending public schools (Matlesky 127). The Court argued that, "a community has the right to protect itself against an epidemic of disease which threatens the safety of its members" (Brandeis 33).
Just as it was over a century ago, the impact of vaccines on public health is the key issue in current debates on mandatory vaccination. If vaccination protects public health, then states have the right to require vaccination as a condition of public school enrollment. Those who oppose vaccination have focused their arguments on proving that vaccination actually hurts public health. Specifically, they argue that vaccinations cause Austim and other developmental disorders (Shiroff and Buckland 79). These arguments are dubious, however, because numerous studies have shown that there is no link between vaccination and autism. In a 2015 report by the CDC, scientists analyzed a sample of over 1,000 children in two group (vaccinated and unvaccinated) and found that vaccination did not cause autism or cause children with autism to develop symptoms earlier (Bekri 346). The study also found that Autism is a "developmental disorder that is present at birth, and symptoms develop during the early childhood years" (Bekri 348). Since Autism is present at birth, nothing that happens after birth (like getting a vaccination) can possibly impact whether one has the disorder.
For more on quoting, paraphrasing and summarizing, see Quoting, Paraphrasing, and Summarizing.
For great paraphrasing examples, see Successful vs. Unsuccessful Paraphrasing.
The simple definition: Plagiarism is copying an author's work and passing it off as your own.
This definition may seem simple, but plagiarism can be much more complicated. Did you know that you could be held responsible for plagiarism if you paraphrase (i.e., to put in your own words) an author's work without providing a citation? Even if you cite your source, if paraphrasing is not done correctly, you could still be plagiarizing.
The purpose of college-level research is to locate and analyze literature created by experts in your field, then process all of the information that you found to create your own original ideas. Citations are important, because they give credit to the authors who helped you develop your ideas. Citations also give your paper authority, because they show that you have read literature on the topic and that your conclusions build upon work of other authors. When you provide proper citations, your professors will see that you understand the purpose of college-level research.