If you’re a photographer, no doubt you do. If not, it’s perhaps not very likely.
It’s the sine qua non for a photo that will be used for anything more than personal use, e.g. sold to someone.
To put it simply (and not necessarily scientifically correctly), it refers to information about a picture. Often this info can be embedded in the file itself. It is things like description text, keyword, copyright information and much more. Tedious things to manage but vital for the picture.
David Riecks is well known to the metadata freaks as the “father” of ControlledVocabulary.com and the publisher of a, yes, controlled vocabulary that many photographers use to help with keywording images.
David has just launched a blog where he will be writing about Photography Metadata.
http://photometadata.blogspot.com/
It will no doubt be well worth reading by anyone working with photo metadata.