Windows 10 upgrade tool?

Just curious does this upgrade my pc or does it give me a clean install of win 10. I just want to upgrade (don't care what you say, its better than 8.1) but dont want to do a clean install and have to reinstall all of my programs. Also I already downloaded the iso to use in case I ever need a clean install, but there is an upgrade windows option and I just want to know if that will upgrade and keep my stuff or if it will only do a clean install.

I used the media tool to upgrade and kept my files.

It just upgrades

The upgrade is not clean. But after you install windows 10 you can go to the update panel and do a clean install without the ISO. Rather nifty.

hmmm not a bad feature. Thank you guys for the help this post will be deleted shortly.

*EDIT never mind I'll keep it here in case anyone else has this quesiton