What is difference between html and htm?

html

Solution

The Web was originally designed by UNIX-centric people, for whom long filenames with arbitrarily long extensions were the norm.

MS-DOS and early versions of windows were limited to 8.3 filenames, so the extension .html was not possible. Microsoft users had to use .htm instead.

Nowadays, there is no reason to use .htm. Use .html in all cases.

Problem

Another newbie question. I just wanted to know what exactly is the difference between html and htm extensions we see for webpages. Are they same? and if so then why two extensions for the same purpose? Thanks

Original source