A GFCI and a circuit breaker are not the same thing.
A "Circuit Breaker" is traditionally an overcurrent device and is designed to protect the WIRING and NOT YOU!!!
A GFCI can break a circuit, but it has nothing to do with overcurrent or protecting the wire. It is designed to protect YOU.
A GFCI is a simple device. It measures the amount of current that passes through two wires (in this case the HOT and the NEUTRAL) and they if they are unequal DOWNSTREAM of the GFCI by more than (usually 20ma) they circuit is disconnected at the point if GFCI installation.
Some CIRCUIT BREAKERS also INCLUDE GFCI (ground fault) and AFCI (arc fault) protection.
I suggest (in the kindest manner) not giving electrical advice if you (by your own words) know nothing about electricity

Happy Reefing