[Google Pixel 6 Pro] V0latyle:
This is where you need to understand the difference.

Bootloader is the first thing that starts on your phone when you power it on. It is responsible for finding and loading the system kernel - literally, it boots and loads - as well as writing images to partitions when flashing. If this is damaged or corrupted, the phone will not work at all, because the bootloader won't start and won't load the kernel (which is in the boot image). Therefore, bootloader is an absolutely critical partition, because if something goes wrong with this, the entire phone is useless.

I cannot stress this enough, you DO NOT want to do something wrong when flashing the bootloader.

The boot image contains the system kernel, the recovery kernel, and ramdisk. This is what the bootloader loads from memory. This is what you patch in Magisk - the patching process modifies ramdisk. If something goes wrong with your boot image, your device will fail to boot, but fixing it should be as easy as reflashing it.

You flash both in bootloader mode. The difference is which image you're using and which partition you're flashing it to. While the bootloader is running, it is able to update its own partitions, as well as write, modify, and reformat any other partition on the device.

To use my Pixel 5 as an example again:

This is how I update bootloader:

fastboot flash bootloader bootloader-redfin-r3-0.5-8906128.img
fastboot reboot bootloader

Reboot is necessary when updating the bootloader; it loads the new bootloader after rebooting.

The syntax here is thus:

fastboot is the program you are using to interface with the bootloader over USB; fastboot only works in bootloader mode and fastbootd mode, while adb is used in recovery and Android system

flash is telling the bootloader what you want to do - in this case, you want to flash a partition

bootloader is the partition you want it to flash, in this case /bootloader. This can be any partition that exists on the device: /bootloader, /radio, /system, /vbmeta, /boot, /dtbo, etc

bootloader-device-buildnumber.img is the name of the file you're instructing the bootloader to flash to the specified partition. It is your responsibility to make sure the right binary goes in the right partition; the bootloader is "dumb" and will simply attempt to flash the specified partition with whatever binary you tell it to, even if it's wrong.

To flash the boot image:

fastboot flash boot boot.img <<< assuming I wanted to flash the factory boot image
fastboot flash boot magisk_patched-25200_xxxxx.img <<< in this case, I'm flashing the patched boot image

Similar to above, this is the syntax:

fastboot is the program you're using to interface with bootloader

flash is the command

boot is the partition, in this case /boot

boot.img is the name of the file you want to flash to the specified partition

Honestly, you're starting to scare me a bit. If you don't know or understand the difference between these two, as I've tried to make abundantly clear, you should not be doing this. Get someone who knows what they're doing to help you.

It is helpful because it automates the commands, but it is NOT a substitute for knowing what you are doing.

Thanks for clarifying, I felt like I was missing something.