Impact Factors - ISI JCR
A journal's impact factor measures how often the articles in the journal are cited. There is a broader definition in the terminology section.
You find a journal's imapact factor in Journal Citation Reports (JCR), a database own by Thomson Reuters and produced by Institute for Scientific Information. Therefore the abbreviation ISI.
Hanken uses a combination of impact factors and the Publication Forum rating when assessing the quality of a journal. Another general assessment tool is Ulrichweb.