Simply put love is an emotion of caring deeply about the welfare of people one deems to be "special" in their life.
The primary difference between parental, sibling, friendship, and romantic love is our sexual desire for those we're in a romantic relationship with. We want physical and emotional intimacy.
Having said that each of us has our own idea of what love is suppose to "feel like", "look like" and how people "in love" should "act like".
Ultimately if one is not being loved (the way they want) they won't "feel loved" no matter what is in the other person's heart. Thus people say: "If you loved me you would...etc"
It's their way of telling their mate what (they) need in order to "feel loved".
Most people are looking for someone to love them (the way they want to be loved). There is no universal definition or way to love.
What one person needs in order to (feel loved) may completely different from what another needs.
Two people who (naturally love the way each wants) is the key.