It is developed and regulated by Esri as a (mostly) open specification for data interoperability among Esri and other GIS software products. In the index file, each record contains the offset of the corresponding main file record from the beginning of the main file.
The main file is a direct access, variable-record-length file in which each record describes a shape with a list of its vertices. An ESRI shapefile consists of a main file, an index file, and a dBASE table.
