Baby, don't hurt me, don't hurt me, no more!
(Omg, i trolled....i will go to hell now)
But seriously for a sec. Loving someone is when you want someone to be happy and you greatly care about this person. If this is romantic/partner love it means you want to share your life with this person and make this person your 'full time friend and part time lover'. If monogamy is your thing than this is that one person you want to commit yourself to and start a family with, you want to see the world and grow old together.
Being IN love is when your brain stops working properly and your entire life seems to suddenly revolve around this person who seems perfect and superhuman in your eyes. You want to spend 24/7 with this person and wear out the bedsprings with him/her. But this fades after a few months, or years. Then you come down to earth and realise the person you left your previous partner for is no better, maybe even worse. Bein in love is like being drugged, it can seriously make you do stupid things and when you come down from your high you realise what mistakes you made.
Falling in love is nature's device to ensure initial attraction and hormone induced 'commitment' to each other so you get to know each other and start making babies. Actual love comes after this and this is the kind of love that helps us raise our babies into healthy stable and safe children and for some people also help them live a meaningful happy life, depending on your view on monogamy and love.
Sadly, when we switch to being in a commited long term relationship with a partner, that falling in love instinct can still randomly kick in.