Webometrics is The study of the quantitative aspects of the construction and use of information resources, structures and technologies on the Web drawing on bibliometric and informetric approaches (Björneborn & Ingwersen, 2004, p. 1217; Thelwall & Vaughan, 2004). This field mainly concerns the analysis of web pages as if they were documents.
Altmetrics – “The study and use of scholarly impact measures based on activity in online tools and environments” (Priem, 2014, p. 266). Also called scientometrics 2.0, this field replaces journal citations with impacts in social networking tools such as views, downloads, “likes”, blogs, Twitter, Mendelay, CiteULike.
Basically, altmetrics is garbage as far as scientific impact is concern. The Top100 papers for 2014 showed it quite plainly, most of the "top articles" being cute, sexy and funny (IgNobel type) but certainly not top notch science. See by youself: http://www.altmetric.com/top100/2014/ (I like #8: Searching the Internet for evidence of time travelers…)
Altmetrics studies the influence of papers (or any subject) in the world wide web such as social networks, web sites,weblogs, news and etc. Webometrics studies the activity of sites (academic websites) in the world wide web based on their papers,backlinks, domain refers, pdf files ,doc files and size of the site.
Thank you all for your answers. I checked the link you provided,Jean-Daniel, and there many of the top-100 that are cute and funny as you said, I think this is because the metrics are based mainly on social networks which are open for all to use, not only academicians and scientists,
Webometrics is (a) a set of quantitative techniques for tracking and evaluating the impact of web sites and online ideas and (b) the information science research field that developed these ideas. Webometric techniques include link analysis, web mention analysis, blog analysis and search engine evaluation, but from the perspective of digital library evaluation the main method is link analysis.
But, Altmetrics is the latest buzzword in the vocabulary of bibliometricians. It attempts to measure the “impact” of a piece of research by counting the number of times that it’s mentioned in tweets, Facebook pages, blogs, YouTube and news media. Thanks