What has happened to the file when I entered "mv file.txt ../"?

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http://unix.stackexchange.com – I wanted to move 'file.txt' one folder up, but instead of mv file.txt ../file.txt I entered mv file.txt ../. Now the file is gone and I didn't get any error message. So it seems the some action was done successfully. But what happened here? I have backups, so at least that's no problem. But I'd like to understand what I did and if I changed anything or if this file magically disappeared. (HowTos)