The H-index is a combined measure of a researcher's individual productivity and influence, based on papers published and the number of citations to those papers. It was developed by Jorge Hirsch, a physicist at UCSD, in 2005. (citation)
The H-index is determined by finding the distribution of citations to an author's publications, and identifying the minimum number of papers that have received at least that same number of citations in other papers. A scholar with an H-index of 7 has published 7 papers each of which has been cited at least 7 times.