File type: Hexadecimal Source
There are 2 different types of HEX files, binary and text-based. The text based HEX files can be opened with any text editor like notepad whereas one needs hex editing programs to open their binary counterparts.
These files generally contain program settings along with their configuration information.
They can also be general data saved in the hexadecimal format which can be stored either as a text file or as a binary format.
It is not a runnable program and double clicking on this file will launch either the text or binary editor depending on the format of the HEX file.