Rear brake balance (+5): allows more rotation of the car during braking, reduces tire wear a little bit on front tires, but your car will slide more when braking + turning.
Front brake balance (-5): creates more understeer when braking, increased tire wear on front tires, reduced tire wear on rear tires, will help prevent sliding when braking + turning.
FR cars usually need more rear bias for better trail braking (turning while braking)
MR cars might need more front bias, to prevent too much oversteer when turning + braking
AWD cars I think need more rear bias to help rotate better when turning + braking
FF cars also need more rear bias to rotate better when turning + braking and also helps reduce front tire wear