GFCI vs AFCI is the code question homeowners meet mid-renovation, usually as a line item they did not expect. The confusion is fair: two acronyms, both breakers or outlets, both trip. But they exist for different disasters, and knowing which is which explains where the code wants each one.
GFCI protects people
A ground fault circuit interrupter watches the current going out against the current coming back. If they differ by a few thousandths of an amp, some current is leaking somewhere it should not be, possibly through a person, and the GFCI cuts power in a fraction of a heartbeat.
That is why GFCIs live wherever water lives: bathrooms, kitchens, exteriors, garages, anywhere near a tub. They are the reason a dropped hair dryer is an anecdote now instead of an obituary.
AFCI protects houses
An arc fault circuit interrupter listens for the electrical signature of arcing: current jumping a gap at a damaged wire, a loose terminal, a nail through a cable, a cord crushed behind a couch. Arcs make intense local heat, and most house fires that start in wiring start as an arc. An ordinary breaker cannot see arcing at all, because an arc rarely draws enough current to trip on overload.
Modern code wants AFCI protection on most living-area circuits, bedrooms first and outward from there, which is why a renovation that opens walls usually brings AFCI requirements with it.
The practical version
In the GFCI vs AFCI split, one watches for electricity escaping through you, the other for electricity misbehaving inside the walls. New work gets whichever the location calls for, sometimes both in one device. In an older house, nobody makes you retrofit overnight, but every circuit we touch gets brought up to what the code asks, and a nuisance-tripping AFCI is worth a proper repair diagnosis rather than swapping for a plain breaker, because it may be reporting something real.