The description of chm format expansion
The chm file is the reference documentation, gathered and stored in the compressed HTML-format. It can include text, images and hyperlinks. Also CHM-file can be viewed in the web-browser. The CHM file object can be applied by Windows and other programs as an online-help.
NOTE: Some CHM files can be opened via the web-browser, as well as the others – via the CHM editor or CHM viewer app.