Source refers to the origin of the resource. For articles, source is the journal title. Not all journals are created equally and the terms below will help you evaluate the quality of the information source.
The terms peer reviewed, refereed, or juried all mean esentially the same thing. Some databases let you limit your results to peer reviewed articles, but not all. It's important to know where to look to determine if a journal is peer reviewed.
A journal impact factor is a ranking that attempts to quantify a journal's impact in it's discipline.
How impact factors are calculated: Three years worth of data are used to calculate the ranking for one year. The 2009 rankings are currently available.
A = the number of times articles published in the journal during 2008-9 were cited by other journals during 2010
B = the number of articles or reviews that were published in the journal during 2008-9
2009 Impact factor for a journal = A/B
Note: When using impact factors to evaluate a journal keep in mind: Comparing journal across disciplines is problematic, when evaluating a journal against other journals, only do so within the same discipline.
Example: Comparing an occupational therapy journal with a biomedicine journal that is used in several disciplines (like Cell) would be misleading.
Type of publication refers to both the format (book, journal, magazine, conference proceeding, dissertation) and the type of publication within the format (report of original research, review, meta-analysis, systematic review, case report, etc.)
Just because something is published in a peer reviewed journal does NOT mean that it is peer reviewed.
Comments are usually letters, or articles, written in response to a previosly published article. They may be written by experts but are likely opinions, not research peices. Even if they are included in peer reviewed journals, this type of content is NOT peer reviewed.
Editorials are articles, or thought pieces, written by a member of a journal's editorial board. Even if they are included in peer reviewed journals, this type of content is NOT peer reviewed.
Reviews are overviews of diagnoses or interventions or research written by an expert who has surveyed the literature, but may or may not refelct rigorous synthesis. These generally are peer reviewed.
Reports of Original Research:
These are the result of investigations to discover new knowledge and can employ a variety of methodological approaches. These are peer reviewed.
Research summaries are literature reviews that identify, appraise, and synthesize quality studies that focus on a single question or clinical topic. Examples include systematic reviews and meta-analyses.