You can read about the Dublin Core Metadata Element Set at https://en.wikipedia.org/wiki/Dublin_Core
It is a set of fifteen "core" elements (properties) for describing resources. DC:title is one of those elements, all of which are listed at Wikipedia.
This fifteen-element Dublin Core has been formally standardized as ISO 15836, ANSI/NISO Z39.85, and IETF RFC 5013. The core properties are part of a larger set of DCMI Metadata Terms. "Dublin Core" is also used as an adjective for Dublin Core metadata, a style of metadata that draws on multiple RDF vocabularies, packaged and constrained in Dublin Core application profiles.
The resources described using the Dublin Core may be digital resources (video, images, web pages, etc), as well as physical resources such as books or CDs, and objects like artworks.
Dublin Core metadata may be used for multiple purposes, from simple resource description to combining metadata vocabularies of different metadata standards, to providing interoperability for metadata vocabularies in the linked data cloud and Semantic Web implementations.