Love is an emotion. That is, to say, a physiological, psychological and hormonal response to certain stimuli. It involves a mess of hormones, oxytocin, endorphins and whatnot, and brain activity akin to a seizure.
We know how people experience love, through brain scans and tests. We also have a good idea of why the different types of "love" evolved in our species and other mammals.
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A species that "loves" its off-spring and nurtures them is more likely to survive. Parental nurturing allows the young of the species to finish their development ex utero. So instead of the mother being saddled with a baby bump for twice the period of time, they can have a relatively short pregnancy and then, whump, out comes baby. A mobile mother is less likely to be taken down by predators than a pregnant one.
It doesn't matter to the jellyfish, but then... who hasn't evolved in hundreds of millions of years and who's the global apex predator/consumer, again?
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Love in the platonic sense... as love between friends, "bros" and family... cooperative love, helps species survival. That one's a no brainer. It's why humans form tribes, dogs form packs, dolphins form pods. While it may seem that a dog or a chimp has little choice or freedom inside an authoritarian pack or gang, there's no physical barriers that keep them within said pack.
Of higher order animals, none are as successful as those that practice pack or herd behavior. It's instinctual and in-bred. Doesn't change the fact that the members of these packs do feel genuine affection for each other. Just ask your dog.
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As for "love" in the sense of "romantic love", that one's pretty obvious. Think about the "seven year itch." How long does it take to father a child, watch it be born, and stay with it long enough for it to be fully mobile and able to forage for itself beside its mother? Seven years is a pretty good estimate.
Sexual attraction and behavior have their evolutionary roots and uses. Women are generally attracted to men with power. "Cute butts" top many womens' lists of desirable traits... those butts mean strong legs and a good hunter. Men generally prefer women who are well-endowed with child-bearing hips. There is also a connection between men who desire power and who are actively polygamous, too.
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Just because we can explain love and its uses doesn't mean we can't enjoy it.
Do I know that the absolute feeling of joy I get when I hug my wife or child is a pre-programmed biological response involving the release of endorphins triggered by touch?
Yes.
Does it matter?
Absolutely not.