Basically when you uninstall an app, it pops up asking if you want to turn it into a ghost. If you select yes, it stores the apk on your sdcard, and adds the app to its list of ghosts. When you want to install simply click on the ghost in the list. I use it to keep my phone clean, and if i download an app, but it doesnt yet have the features i want, i ghostify it. Top app, the developer seems very helpful and open to ideas too.