Quite a brief post on Metadata.
I remember in one of my job-interviews when I was asked if I had knowledge of Metadata. I sure did say !yes! I know all about annotating webpages, I know Metadata concept was related to databases and there is a classical example of metadata and I also knew Dublin Core which I had used to create a Minimal Repository Implementation of OAI-PMH. Apparently we know less then we think we know most of the time. Metadata is quite a discipline of study and these 2 references give a very good overlook of what Metadata are.:
Day, M (2005) “DCC | Digital Curation Manual”, Metadata Retrieved February 5, 2012, from http://www.dcc.ac.uk/sites/default/files/documents/resource/curation-manual/chapters/metadata/metadata.pdf
NISO Press|National Information Standards Organization “Understanding Metadata” http://www.niso.org/publications/press/UnderstandingMetadata.pdf