Selective Attention

I've always been somewhat bothered by this term because it seems somewhat redundant to me...see what you think. Selective attention is purposely focusing your conscious awareness onto a specific stimulus. This means that if you are in a noisy place with lots of people and you purposely pay attention to the person you are speaking with, you are engaging in selective attention. Easy enough, right? So how is this different from "paying attention" or simply "attention"? I know there are subtle differences, but it seems redundant to me.