What are "Equalizer Terminals" in the room? What is it?

The full name is "equipotential connection terminal", which means that all the metal structures inside the building are connected together to form equal potentials, so that in the event of a leakage of electricity, the potentials at each point in the room are equal, so that no current will be generated (no potential difference).

Equipotential connections are required in high-grade buildings to ensure the safety of the occupants. In the bathroom you can connect the equipotential connection terminals (in the connection box) to the shell of the electric water heater, washing machine, etc. So that even if there is a leakage of electricity, it will not cause any harm to people, and you can take a shower with the electric water heater on without fear or hesitation.

To put it plainly, even if your electric water heater shell is electrified, you can touch it with your wet hand, and you will not be electrocuted!