"Bad" Bad bishop
"Good" Bad bishop
A bad bishop is the bishop on the same colour complex as its central pawns. 'Bad' is not an assessment of quality, merely a descriptive term.
In position 1, we see a bad 'bad' bishop. It is completely locked out of the game, leaving white effectively a piece up and giving him a free hand to attack on the kingside.
In position 2 we have a good 'bad' bishop defending its center pawn. White's good bishop, on the other hand, will not be able to defend its center pawn on d4 should it come under attack.
Bad bishops protect good pawns.