The h-index measures an individual's citation count over time. When looking at the total article output for an individual, the h-index is the number of articles that have at least that number of times. So if an individual has an h-index of 9, that means they have 9 articles that have been cited 9 or more times. The higher the number, the better.
Originally, proponents of the h-index claimed it was a better way to compare individuals' output when those individuals were at different career points. However, the h-index also appears to favor those with longer careers and therefore, more publications, just as the total citation count does. Take into consideration the number of publications and career length when comparing individuals' h-indexes.
Data contained in Experts.ASU is derived from Elsevier's Scopus database. As the name implies, only data for ASU faculty is available; for authors not in Experts.ASU, use the Scopus database to obtain an h-index. Because the data comes from the same source, you may compare h-indexes from Experts.ASU with h-indexes from Scopus (provided the authors are in the same field and at the same career level.)
The h-index derived from the Web of Science database is calculated only from journal articles and does not count citations from conference papers, books or book chapters.