HTML in HTM : Experience?

Question

I've been exploring a few ideas around file extensions, and I came across this HTM extension where you can implement HTML and VBS.
It looks like an application and I've been playing with it.
My questions are:
• Does anyone have experience in this area?
• Would you recommend using .HTM for client-side help service, or .HTML?

Answer 1

HTML and HTM are same extension... second is inherited from times when filename were limited to 8+3 characters dot separated, first is the natural one in modern file systems ^^
On the other hand, VBS (Visual Basic Script) was an alternative to Javascript on user side, only supported by Internet Explorer (for obvious reasons), but seems to no more be supported in Edge...
Another Microsoft specific format related to Html was .MHT (web archive -- embed whole page and dependences/ressources in one proprietary file), wich could make thinking to looking "like an application"... but these files (.mht and/or html code embeding vbs) are highly dependent of Internet Explorer, and can't run in anyelse environment ;P