How op-amp can be used as adder?

An operational amplifier (op-amp) can be configured as an adder using a summing amplifier circuit. In this configuration, multiple input voltages are fed into the inverting terminal through resistors. The op-amp produces an output voltage that is proportional to the negative sum of the input voltages, scaled by the resistor values. By using feedback and appropriate resistor ratiOS, the circuit can be designed to add the input voltages with desired gain or weighting.