"It" the "one from Amethyst"

Which QR?

An Npub QR?

An Nevent QR?

A Lightning QR?

A Cashu QR?

Some random QR someone posted?

YOU were not very descriptive and effectively said "What happens when you scan some information on the internet with a Nostr client app on your phone?

Literally anything could happen because a QR is just visual data.

-With an Npub QR it COULD open a browser URL to an Njump profile or if you disable opening QR links your phone could say "no usable data"

-With an Nevent it COULD open a browser URL to an Njump event link or if you disable opening QR links your phone could say "no usable data"

-If it's a Lightning QR it could launch a Lightning app or if you disable opening QR links your phone could say "no usable data"

So, do you see how my answer was non-specific yet trying to help? Yet, instead of realizing that your question was not very good, you blame me.