ISI JCR - Journal Citation Reports

Impact factor: measures the frequency with which a journal has been cited in the last two years. It is used to compare journals and evaluate the relative importance of a journal within the same field of science.

Quartile: If the list of journals in the same category, arranged from highest to lowest impact factor, is divided into four equal parts, each of these parts is a Quartile. The journals with the highest impact factor are in the first Quartile.