If you choose "Hidden" a partition/volume is made starting on LBA 256 and the fourth partition entry is filled with it's addresses in the MBR. (at first sight I can see very little "hidden" in this)
If you choose "Deep Hidden" a partition/volume is made starting on LBA 256 BUT NO partition entry for it is made in the MBR. (at first sight I can see nothing "hidden" in this but a simpler NOT addressed volume).
BootIce also creates n bootsectors with various amounts of "hidden sectors" all - by difference - pointing to the same filesystem (how these are used during booting I don't know).
Basically you can access the "Deep Hidden" filesystem (if you are working on an image) by mounting the image in IMDISK manually (giving it the 256 "blocks" offset. or, if you are using a "real disk" by creating temporarily a partition entry for it in the MBR.