The Day Bill and Melinda Gates got billions from Warren Buffett: "We cried"

The transcript describes a conversation about an unexpected gift of billions, leading to an emotional response and reflection on the impact of such generosity. The speakers express gratitude and discuss how this generosity will enable them to do more for people worldwide. The conversation ends with a touching moment of friendship.

What does the speaker mean by 'unbelievably touching moment'?

What themes are present in the speaker's reflection on their experience?