You will encounter many types of articles and it is important to distinguish between these different categories of scholarly literature.  Keep in mind the following definitions.

Peer-reviewed (or refereed):  Refers to articles that have undergone a rigorous review process, often including revisions to the original manuscript, by peers in their discipline, before publication in a scholarly journal.  This can include empirical studies, review articles, meta-analyses among others.

Empirical study (or primary article):  An empirical study is one that aims to gain new knowledge on a topic through direct or indirect observation and research.  These include quantitative or qualitative data and analysis. In science, an empirical article will often include the following sections:  Introduction, Methods, Results, and Discussion.

Review article:  In the social sciences literature, this is a type of article that provides a synthesis of existing research on a particular topic.  These are useful when you want to get an idea of a body of research that you are not yet familiar with.  It differs from a systematic review in that it does not aim to capture ALL of the research on a particular topic.

Systematic review:  This is a methodical and thorough literature review focused on a particular research question.  It's aim is to identify and synthesize all of the scholarly research on a particular topic in an unbiased, reproducible way to provide evidence for practice and policy-making.  It may involve a meta-analysis (see below). 

Meta-analysis:  This is a type of research study that combines or contrasts data from different independent studies in a new analysis in order to strengthen the understanding of a particular topic.  There are many methods, some complex, applied to performing this type of analysis.

From Tutorial: Scholarly Literature Types, Cornell University Library