True love is when the person you love unconditionally feels the same way about you, where you know you can trust each other and never want to be with anyone else ever again.
It can be instant 'love at first sight' and can also grow over time.
mom-"True love is very rare."
girl-"I know mom, I know, that is why I shall cherish him forever. I'll cherish him past death, love him for who he is."