Love

salam..
i've been wondering, a lot of people are really into relationships, and finding this so called, 'love'.
my question is simple; what is love ? what difference is love towards ur family, and towards the opposite sex ?
is it really love, or is it lust ? why do we search for love ? why why why ?

with all due respect; for those in relationships, please enlighten me. =)

PS : by love, i mean love towards the opposite sex. we all can understand love and affection towards our family, right ?