The impact factor or journal impact factor of an academic journal is a measure reflecting the yearly average number of citations to recent articles published in that journal.
An academic or scholarly journal is a periodical publication in which scholarship relating to a particular academic discipline is published.
Broadly, a citation is a reference to a published or unpublished source.
How to Find the Impact Factor for a Journal by Roy E Brown
It is frequently used as a proxy for the relative importance of a journal within its field; journals with higher impact factors are often deemed to be more important than those with lower ones.
Web of Science-Journal Impact Factors by smswanberg
The impact factor was devised by Eugene Garfield, the founder of the Institute for Scientific Information.
Eugene Eli Garfield was an American linguist and businessman, one of the founders of bibliometrics and scientometrics.
Impact factors are calculated yearly starting from 1975 for journals listed in the Journal Citation Reports.