According to the Cochrane Handbook for Systematic Reviews of Interventions:
"A systematic review attempts to identify, appraise and synthesize all the empirical evidence that meets pre-specified eligibility criteria to answer a given research question. Researchers conducting systematic reviews use explicit methods aimed at minimizing bias, in order to produce more reliable findings that can be used to inform decision making."
In other words, a systematic review is a literature review that is researched according to strict parameters in order to reduce bias.
Types of Systematic Reviews:
The Cochrane Library is a collection of six databases that contain different types of high-quality, independent evidence to inform healthcare decision-making. All six databases are searched at once and you will find links to systematic reviews in the first and second tabs in your results list, if any have been published on your topic. You will have access to the full-text of all Cochrane Reviews found in the first tab, but only summaries for the Other Reviews found in the second tab.