BibTeX has been widely in use since its introduction by Oren Patashnik 20 years ago. As the name suggests, it was intended to be used in combination with the typesetting system LaTeX, but it has become possible, for instance, to include BibTeX-bibliographies even in Word-Documents using third-party tools.
BibTeX utilizes a plain-text file-format which can be created and modified using an arbitrary text-editor by the user. There are tools in existence which provide a more convenient UI.
The word ,,BibTeX” stands for a tool and a file format which are used to describe and process lists of references, mostly in conjunction with LaTeX documents.
Here you can learn about the BibTeX File Format, How to use BibTeX and BibTeX Tools which can help you to ease your BibTeX usage.