What does it mean its better to have loved and lost then not to have loved at all?

He means that it is better to have been in love at some point, as it is a great powerful feeling, rather than never being in love, and had that powerful feeling in your life. As every experience in life, you learn from it, and being in love is a learning experience. Even if it does not end the way you wanted or planned, at least it will Excel your life experiences, and teach you in the future.