That is because the first two at least are not detailed topics. So really there isn't much to say.
PXE Holding Queue - You can add a device to the holding queue. This means that the next time it PXE boot, Managed WinPE Boot will be the default option.
Bare Metal Server - Probably misnamed by the Server Manager team. This really is just the ability to add any computer (server or workstation) by MAC Address to the database. So if you buy some computers from dell, you can put them in the DB before they get their or before you have to image them. Look up CSVImport. It is pretty much the same thing.
Not sure what you mean by PXE Provisioning, I don't have a Core in front of me. But do you mean PXE Booting and using Provisioning? If so, there should be a BKM for Provisioning.