This can't be summed up in just a few words.....
Well, there are many types of love... romantic love; the agape love we have for our children; the type of love for friends, pets, and even intangibles such as love for the sight of a sunset......
But I think you're referring to romantic love, so I'll tell you what I think of that. In romantic love, it's wanting to share the aspects of your life with this person, from the big things down to the little everyday happenings. When you think to yourself, I can't wait to tell (his name here) about what happened today..... and knowing that this person is thinking of you, too. It is trying to protect each other from harm, caring for them, being there for them no matter what. It is in doing little things for each other everyday, as a courtesy and as a help. It is knowing you can count on each other to be in your corner, even when no one else is, especially in public.
In romantic love, you don't need to be with each other every moment to feel secure. It is being comfortable in silence and stillness as well as during verbal (and sexual) sharing. It is a look exchanged between the two of you that says you are my everything, without using words. It's hoping the other will be there so you can help and enjoy each other as you grow old.
Ultimately, imho, true love is wanting the other person's happiness and well-being, more than you want it for yourself, and doing everything in your power to see that they get it.
Well, that's my take on love... what's yours?