File folders turn into exec files
On a school iMac, I created folders which contained html, jpg, pdf files and other folders. I copied these folders to my thumb drive (the one I use all the time). When I got home, I put this thumb drive into my iMac (Yosemite OS) to finish the folder transfers. When I found the folders I was looking for, they had turned into exec files. What happened?
iMac (27-inch Mid 2011), OS X Yosemite (10.10)