Metadata generally refers to data that describes, or is about, other data. As such, it may include information about the acquisition or publication of the underlying data, or technical aspects like the format of the files, the amount of storage they require,
or of other properties of the data, and whether they are released under a license that permits reuse or not.
A typical example would be bibliographic metadata, in which key properties of formally published materials are collected — author, title, journal, issue, DOI, PubMed ID, PubMed Central ID or a summary of the content of the published item:
What if everyone in the world were in your lab – a 'hive mind' of sorts, but composed of countless creative intellects rather than mindless worker ants, and one in which resources, reagents and effort could be shared, along with ideas, in a manner not dictated by institutional and geographical constraints?
Other common types of metadata include access codes to database entries, e.g. the access number for a gene listed in Gene Bank.