"EndNote is a commercial reference management software package, used to manage bibliographies and references when writing essays and articles. It is produced by Clarivate Analytics (previously Thomson Reuters)." – Wikipedia
In a nutshell, EndNote manages references, images, notes and other files in an encapsulated EndNote library.
EndNote's Cite While You Write feature links references to a Microsoft Word document and automatically generates a reference list/bibliography.
EndNote offers a wide variety of output styles including specific journal styles.