I asked this question back several months ago. Everyone has their own definition of love. But usually, "I love you" is more of a...friendship sort of thing, I suppose? It isn't in the deep sense where you would do anything for this person, and they are the most important thing in the world.
Being in love, is exactly that. This person is by far the most important person in your life, you put them up on a pedestal, and you will do whatever you possibly can to make sure that pedestal stays nice and tidy.
Others might and will disagree with that I'm sure, but that's always how I've looked at it.
Side note: As discovered from recent events, being in love is a two way street. One can feel they are deeply in love, while the other just loves them as a friend and doesn't want to see them get hurt. That shit sucks when it doesn't work out properly. Be careful when it comes to expressing love towards someone.
QUESTION
What's the difference between "love" as in "I love you"
and
"In love" as in "I'm in love with you"?
You can be "in love" with one person.
You can love everyone.
Also this. Definitely.