Differences between program on laptop and application (app) for a windows tablet?

A friend said that when i code a programm for win8 for my laptop, i won't be able to run it on his tablet because it's not yet an "app".
But when i create an app for a tablet i'm able to run it on my laptop.

(obviously i'm not searching philosophical answers regarding the terms "programm" or "application".)
(posts from the new user that recently bumped about 10 old topics will be ignored)
(i won't donate for this topic, so don't write a lot of stuff as answer. just get your +1 while having fun with sharing your knowledge)

Windows tablets suck.

If it's win8 I'm fairly certain the computer os can run w8 apps and programs, but the tablet version of os only runs apps.

There's a large chunk of the WinAPI distributed in PC OS's that just isn't part of the one distributed for tablets. A software built for tablets will be compatible on desktop Windows but something built on a desktop OS may very well access ressources and api calls that aren't supported by tablets. I'm pretty sure Win8 portable binaries are available for VS2012 and later. This will allow you to target your build platform for tablets from the desktop GDI.

ok thanks guys,
topic can be closed!

Windows Mobile is actually better feature and usability wise than other platforms now, they have done amazing catch up work. so They are worth looking into.