Understanding a journal's impact can help researchers find the best journals to place their work. It can also help direct students and faculty to the top journals in their field for research.
Journal rankings and impact factors are quantitative measures for journal evaluation, within its field or discipline. Interdisciplinary journals may have rankings in more than one field.
In general, the number of citations within a certain time period drive a journal’s impact factor, conferring an importance to the research published within. But it’s important to remember that although it might seem as if some of the methods of evaluation are an exact science, recognizing the strengths and weaknesses of each tool gives a broader view of a particular journal and its performance.
Keep in mind:
In scholarly and scientific publishing, altmetrics are non-traditional metrics proposed as an alternative to more traditional citation impact metrics, such as impact factor and h-index. The term altmetrics was proposed in 2010, as a generalization of article level metrics, and has its roots in the #altmetrics hashtag (from Wikipedia).