What needs to be on a USB such that you could hand it to someone and gift them a discrete amount

[Bitcoin]

What needs to be on a USB such that you could hand it to someone and gift them a discrete amount

This may be a very stupid question. I was watching an interview with Nic Carter (https://youtu.be/mDyBbGCiBUU?t=1094). In it he gives Lex a present of a USB with $100 worth of Bitcoin. What is actually on this device that allows Lex to claim the $100?

My understanding of storing Bitcoin on a USB is that only your private key is on it, and all your transactions (linked to your public Bitcoin address) is on the Blockchain, which is public, and your private key along with your public Bitcoin address allows you to claim some amount of Bitcoin. So I guess this is the first part of the question, and what is on Nic's USB is the second part...

Source: What needs to be on a USB such that you could hand it to someone and gift them a discrete amount