What is a BIOS whitelist request , BIOS mod and BIOS unlock?
BIOS Whitelist Request
Some BIOSes have options within them which are "whitelisted" ie cannot be toggled. Some people want to toggle these options (eg fan speed,WWAN and wireless cards) so request the BIOS options to be "un-whitelisted".
Example:
From here
...Many manufacturers such as Lenovo and HP uses a list called "White-list" in their machines BIOS to limit what peripherals you can use.
From Beware the Dreaded White-List
So basically it's a list of "acceptable hardware" that may be installed in the computer. The most common internally installed piece of hardware is the network (Wifi) card, which is an optionally installed device that goes in an internal PCIe slot.
The thing is that if you swap the network card, upon booting the computer will check to see if that WiFi card is in the "white list". If it isn't, the computer WILL NOT BOOT.
BIOS Modding
3rd party modifications of the official BIOS, involving 'flashing' of the BIOS, which is very risky for the inexperienced May void your warranty. Failure in flashing the BIOS may "brick" your computer. Attempting to mod an RSA-signed BIOS (HP) will almost certainly cripple your computer.
Community example: bios-mods.com.
BIOS Unlocking Request
Request to enable to toggling of the whitelisted options in the BIOS. Some BIOSes don't even have the options whitelisted - they are just not displayed; hence people request so that a modded BIOS is made with the options added to the menu. For example, my Insyde H20 BIOS for my Acer laptop does not have an option to enable VT-X, so despite the CPU supporting VT-X I can't use it (though I got it to work eventually without using a modded BIOS).
Basically BIOS Whitelist Request is the same as BIOS Unlock, and to achieve that you use modded BIOS in place of the officlal manufacturer's BIOS.
A BIOS whitelist is a specific list of PCI-Express network/wi-fi cards that are allowed to be installed in a laptop. Only cards in this list can be used in the laptop, other cards will produce an error message on boot prompting you to remove the unauthorized cards.
See this related question: Why do some Centrino chipsets and PCI-Express cards say Not for Lenovo/HP?
BIOS mods are 3rd party modifications of the official BIOS. They are often tweaked to remove this whitelist, therefore allowing any network card to be installed. They sometimes add other features as well, such as the ability to access more detailed configuration settings in the BIOS than would normally be allowed.
Note that these BIOS mods are not supported by the manufacturer, and will most likely void the computer's warranty. They also carry the risk of bricking the computer and leaving it in an unusable state.