A systematic review is a summary of all of the literature on a particular topic, that meets pre-defined eligibility criteria.
The Cochrane Collaboration definition:
"A systematic review summarises the results of available carefully designed healthcare studies (controlled trials) and provides a high level of evidence on the effectiveness of healthcare interventions. Judgments may be made about the evidence and inform recommendations for healthcare.
http://consumers.cochrane.org/what-systematic-review
Five steps in a systematic review:
1. Formulate your question
2. Search for studies
3. Assess the quality of studies
4. Summarise the evidence
5. Interpret the findings
Would you like to see some examples of systematic reviews? The resources below are useful for locating systematic reviews:
Quickly identify systematic reviews for decision making. This resource brings together details of systematic reviews indexed in a range of different research databases.
Run your search and then refine by evidence type on the right hand side. The options include systematic reviews.
The Cochrane Library includes evidence from Cochrane and other systematic reviews, protocols and clinical trials.
Run your search, and then from the options on the left hand side, select Types of information and choose from a list that includes systematic reviews and guidelines.
Run your search and then refine by article type. Click on more to see the full list.
Also try PubMed Clinical Queries (select from the home page of PubMed). Run a search for a topic, and the systematic reviews will be displayed in the middle column.