Your hardware ID(HWID) is a set of identifiers that anti-cheats use in order to determine who you are.
These identifiers are based off of the pieces of hardware you have inside your computer. For example, your motherboard has a specific serial assigned to it, and the only way to change that is by spoofing it or getting a new motherboard.
A spoofer is a piece of software that gives you a new HWID. Usually, a spoofer will have to be ran every time you restart your system, depending on which spoofer you use.
You do NOT always need to use a spoofer. If you have never been HWID banned from the game you are playing, and your cheat is fully undetected, then you will not need a spoofer. If you do get HWID banned, you will however then need to spoof your HWID so that you aren’t instantly banned.
It is also advised to ALWAYS spoof to avoid getting your default HWID getting banned.