can't put anything on my 'desktop'

i am not sure what i did ... i was cleaning things off my hard drive and deleted a few files titled 'desktop' thinking they were copies or something , and now I can no longer put anything on my 'desktop' ... when i try to open a file on the desktop it tells me that it can't open it b/c it is 'in the trash'. Also, when i open the HD, the desktop is no longer in the side bar (with apps, etc.).

So, in order to work with the files that I previously worked on from the desktop, I have moved all of the files from my desktop into the hard drive and can work from there, but can no longer just put files for daily working on the desktop...

help!