Here's a nice definition that I found online:
" Camp (n.) and Campy (adj.): Being so extreme that it has an amusing and sometimes perversely sophisticated appeal. Over the top and farcical, intentionally exaggerated so as not to be taken seriously. Found primarily in television, theatre and motion pictures, camp endeavors for satire and, for those who fully understand and appreciate the risible nature of its material, it's not surprising when it develops a cult following.
Both 'The Little Shop of Horrors' and 'The Rocky Horror Picture Show' are movies widely considered very campy, particularly to those of my generation. "
In short, campy is extremely satirical and stereotypical. It's super-comical.
Or, in other words, it is a complete, obvious joke. No attempt whatsoever at being serious.