information about an item, rather than the information in the item itself
A description of the instrumental setup, containing but not limited to, relevant timerange, source parameters, receiver setup parameters (especially LO frequencies, and the switch settings used to select bands and filters), the observing proposal in aid of which the observation is made, the observing procedures involved.
Literally "about data", this terms refers to searchable index fields used to organize a body of larger documents, objects or content. For instance, in a searchable archive of image files, the "meta data" would refer to searchable fields such as artist name, title, year and so forth; the "content" would be the image file itself. For a news archive, the metadata would be the date, author and topic, and the content would be the actual story itself.