Impact factor indicates the number of times the articles in a journal are cited in other studies during a particular period. For example, an impact factor of 3 indicates that each article in the journal was cited 3 times on average during the specified period. It is assumed that an article that is cited many times presents novel, interesting, or important research.
There are various formulas for calculating impact factors. We generally follow the ones published in Journal Citation Reports (JCR) by Thomson Reuters. Most journals have a JCR impact factor in the range 1-4. Brand new journals tend to have low impact factors.