Jacob imprinting? "twilight"?

ok so in breaking dawn jacob says that he "imprinted" on renesmee. so does that mean that he wants to "be" with her like in a boyfriend girlfriend, husband wife type of thing? or that he just cares deeply for her, because i don't understand how he could really love a baby in that sort of way... and how did bella and edward find out the he had imprinted on her because i forgot and how did they react?