The definition to this via the Wikipedia is:
Unrequited love is love that is not openly reciprocated or understood as such, even though reciprocation is usually deeply desired. The beloved may or may not be aware of the admirer’s deep affections. The Merriam Webster Online Dictionary defines unrequited as “not reciprocated or returned in kind.”
To me, it’s that part of a movie where the girl stares at a man across the table longingly and he’s going on about his new love interest – which isn’t her. I do not like those kind of movies as it makes me want to shout to her – “get over it and move on”. It seems weak to me.

In thinking about it longer and more in a reality situation, not a movie, I wonder just how powerful unrequited love can be. Is it truly a weakness? Or does the person who refuses to confess how they feel stronger somehow for holding on to it?
I’ve no idea.
Unrequited love can be excruciatingly painful. Maybe the person just wants to feel the love for another, and not want to go through the sorrow of a possible heartbreak.
I’ve no idea.
It’s an interesting thought though – to love someone so much you have chosen to keep it inside and have it melt through you like acid?
No thanks.
Who am I kidding, we all probably go through it once in our lives. Could you imagine if you wanted someone so badly, kept it to yourself and in some fairy tale moment your knight or princess shows up to tell you their secret “they’ve loved you all along”. Great ending for a story, don’t you think?
Reminds me of first love.

If he/she isn’t interested in you the way you are interested in them, do move on. It’s not good to think about or hold on to feelings for someone who doesn’t want you in the same way.
Move on.