I'm only have a vauge understanding but I'll give it a shot.

x86 is a CPU architecture. ARM, PowerPC, RISC are other types A CPU architecture is like a standardized set of instructions.

Here's a horrible attempt an analogy based on buildings. Let's say there's only 2 types of buildings on earth:

Type A buildings are very tall and use an elevator to go up many floors. Each floor has just one room.

Type B buildings have a very very long hallway branching off into many rooms but just one floor.

If you wanted to tell someone how to retrieve an item from a Type A building you'd say something like "Take the elevator to floor 3. Grab box 01. Take the elevator to floor 4 and leave it there."

Obviously this wouldn't work in a type B building since there is no elevator. You'd tell the person to walk down the hallway until they reached room 03, grab box 01 and walk to room 04 and drop it off.

That's a very very very very simplified version of how different CPU architectures work. They each have their own "instruction set" based on how they're set up. The x86 architecture is used in most laptop and desktop computers. The new Apple Macs use ARM, as do most smartphones.

Now, a bootloader is the thing that handles everything from when you see your laptop's (or desktop motherboard manufacturer's) logo on your screen to when you see the spinny circle of Windows 10. It handles loading the operating system from a location on disk into the correct place on the computer. So far this step has been secret and proprietary.

The libreboot project is a project to make an open source version but it mostly only works on pre-2008 laptops. This is because post 2008 Intel started asking for a password from the bootloader that only Intel had, making it impossible to put your own bootloader in. Coreboot is a much more limited version of this, whose main focus is to remove a part of the Intel bootloader called Intel Management Engine. The Intel ME has access to your computers hardware unrestricted by the operating system.

I'm not sure what open sourcing their bootloader means for us as a community. If we can finally have libreboot working on AMD x86 computers or if there are many more hurdles along the way.