Bibliometrics is a statistical analysis of written publications. Historically used to rate/rank publications, it was a tool to help libraries make purchasing decisions. Bibliometrics are now also used as a means to gauge a researcher's scholarly publication output and thus, as one tool in deciding retention, promotion, and tenure (RTP). Numbers have been created to rate both publications and authors. Be advised that there are several organizations/individuals that have created the formulas to calculate these numbers and there is no "one place" to get all the numbers available. Also, if you plan to incorporate bibliometrics into your RTP packet, be aware that some of these numbers (e.g. Journal Impact Factor) cannot be applied evenly across disciplines.
So while bibliometrics are widely used as a means of gauging a person's publication quality, the practice remains controversial.
See the San Francisco Declaration on Research Assessment and the European Association of Science Editors statement on inappropriate use of impact factors.