It's the metal plate usually just below the faucet that looks like it might be useless. But it has an opening underneath to let the overflow water in. These are always sized to handle more water than the faucet can output.
This is basically a non-concern in anything but very, very old, unremodeled bathrooms.
The sinks do as well, but it is more obvious.
But the sibling comment to this one, where a sink had an overflow, but it was not connected, did not meet code [also 1].
Go figure. There must be some reasoning there, but I'm confused as to what it is.
https://forms.iapmo.org/email_marketing/codespotlight/2018/m...
So if you have old two-prong outlets in your house from back when, those are allowed.
If you replace them with a three-pronged outlet which is ungrounded, that breaks code.
If the three-pronged outlet is a GFCI outlet labeled with NO ELECTRICAL GROUND, that is allowed.