Provide unique identification and links to organizations, files, or databases.

It is nothng but the information about information in database.... Is called metadata

I can tell you in case you are using Photoshop,open Bridge and select photo then look arround for metadata panel.click on it to expand.If you cant see metadata panel then go to Window-Metadata panel

No. Keywords are not called or known as Metadata in Java

Metadata is "data about data". It is used for two fundamentally different concepts. Structural metadata is about the design and specification of data structures. Descriptive metadata, is about individual instances of application data, the data content.