When there is a current in a resistor, electrical energy is transferred as thermal energy. This is the heating effect of a current. It is an advantage in devices designed to heat things, such as a kettle, toaster, electric heater and oven. Their heating element is a wire with a high resistance, almost all the electrical energy becomes thermal energy, and the heating is easy to control. In a filament lamp the filament gets hot enough to give out light, and in a fuse the wire melts if the current is too large, which breaks the circuit.
The heating effect is a disadvantage when the thermal energy is not wanted. In a computer, a phone charger or a connecting wire, the energy is wasted to the surroundings, so the device is less efficient and costs more to run. Components can overheat and be damaged, which is why computers need fans. Wires that get too hot can start a fire.