The Electronic Relay is designed to eliminate mechanical parts and contacts found in relays. It is more durable and has current limit protection of 45 Amp. This relay will be switched on or off by the ECU and lets battery power through to coils, injectors, fuel pump etc.
Note that a fuse box after this relay is still important to protect certain circuits from over current. 45 Amp can melt thinner wires causing a fire hazard.