"Chuckle" is usually used with mild amusement. He chuckled when he thought of what has happened. "Giggle" usually is attached to some nervousness. The girl giggled when the boy who she liked asked her a question. Also, "giggle" is more often used with females.

Good question, I think this can give you an idea, although the line can be very thin: https://www.youtube.com/watch?v=6gq-bJwNKSw

I think there are a simple different giggle it mean to laugh. In a silly way or loudly or from your heart but chuckle mean to laugh quitely without any sound

Both have the same meaning.