what is the difference between html and htm files

1.html is awesome and new, while .htm was used back in the old days when
2microsoft wanted all file name extentions 3 charectors. But, both of the
3extentions do the same thing. Since microsoft has a big homescreen and
4they got their website since 198 something, there homepage is
5microsoft.com/index.htm.
6
7                       <Thanks for reading>