Say you have multiple bodies in an NX part file and you do not wish to delete a body forever, you can apply a Delete Body feature to one of the bodies which would then allow you to suppress this feature and bring the body back or delete the Delete Body feature and the body will reappear.
In a nutshell, it's a "do over".
If you have a webkey account, I'd recommend downloading the What's New guides for all NX versions you're skipping - or look up the command in the Help documentation, as it should be outlined there.
Tim Flater
NX Designer
NX 8.0.3.4
Win7 Pro x64 SP1
Intel Xeon 2.53 GHz 6GB RAM
NVIDIA Quadro 4000 2GB