BIOS . . . I never really understood it . . . I was also doing something with the pins on the mobo
The moral here is only make one change at a time ! If it all goes pear-shaped after the one change then you know what caused it. If you make two or three changes at the same time - which one is the culprit ?
As has been explained above, the BIOS is the Basic Input/Ouput System and is responsible for starting a computer up.
The pins you refer to are almost certainly the CMOS/BIOS re-set jumper. Three pins with a small plastic connector between two of them. The connector - the jumper - normally stays between two of them and you move it to connect the third pin to re-set the BIOS. This was akin to a 'get out of jail free' card, this operation would re-set the BIOS to default settings if it had got messed up. They have gone out of fashion in recent years because modern UEFI/BIOS include a re-set to factory default option inside them.