Key difference: Loving someone is a feeling of warm personal attachment or deep affection. It can be used to refer to anyone, any person, or any thing. Being in love with someone usually refers to a profoundly tender, passionate affection for another person, mainly stemming from sexual passion or desire.
According to Dictionary.com, ‘love’ is a profoundly tender, passionate affection for another person. It is a feeling of warm personal attachment or deep affection, as for a parent, child, or friend. It can also be used to describe sexual passion or desire.
Loving someone is a feeling of warm personal attachment or deep affection. It can be used to refer to anyone, any person, or any thing. For example: I love you. I love my mom. I love my husband. He loves his girlfriend. I love my dog. They love pizza. She loves vanilla ice-cream. Mary loves the sea. John loves football.
Being in love with someone usually refers to a profoundly tender, passionate affection for another person, mainly stemming from sexual passion or desire. For example: I am in love with my wife. Jill is in love with Jack. Alice believes that she is in love with Mark.
The main difference between loving someone or something and being in love with someone is the manner of usage. Loving has a more general usage and can be used to refer to someone or anything. Being in love mainly refers to a significant other.
Modern usage of the terminology transmits that being in love with someone is a strong infatuation, a powerful feeling of attraction. It is basically the feeling that one feels in the 'honeymoon' period of a relationship, when you want to be with that person all the time, when you think about that person all the time. This feeling can last forever, however it usually lasts anywhere from a couple of weeks to 18 months or so. After this period, the passion usually dies out and the ‘being in love’ feeling is then replaced by either ‘loving’ or the relationship just sizzles out and dies.
Being in love is a high, an exhilaration of feeling, however, one should realize that loving someone is not an absence of passion, its just a different form of it. Loving someone is dedication, respect, the willingness to look past the other person's shortcomings and just appreciate the person. It takes commitment and patience. This is why spouses can still love each other after 10 or 20 years of marriage; it is just harder than it was during the first year: the 'honeymoon' phase of marriage.
However, many modern break-ups mistakenly use the sentence, “I still love you, but I’m just not in love with you anymore.” The error here is that they don’t still actually love that person. What they mean to say is that: the 'honeymoon' phase is over, the passion has died out, and I don’t care about you or this relationship enough to actually put work into it; however, there is some remnants of affection remaining, which makes me think I still love you, but it’s best that we seek the passion and its high somewhere else.
Essentially the difference between ‘loving’ and ‘being in love’ is that ‘loving’ is to cherish, to be kind to, to want to spend time with, to respect, to enjoy, to trust, to want to get to know better. However, ‘being in love’ is to be smitten, infatuated, enamored, hooked, taken with, besotted, be head over heels.