What the 'h' is that index?

Apparently, a physicist at the University of California, San Diego has come up with an index called h-index to help judge the performance of researchers - and, h-index is the highest number of papers that a scientist has written each of which has received at least that number of citations. Thus, h-index of 50 means 50 papers each of which have at least 50 citations. For more information, go here , here and here: Go here for the paper.