Inside GE 200 amp outdoor consumer unit(load center)

Ok since Amercan electric supply is Split-Phase 240 volt with a center tap on pole transformer. Each phases of 120 volt and Neutral to carry unballance back to ceter tap
Portion of transformer u can see L1 and L2 comming In to main 200 amp 240 volt breaker. Then it pass onto inter weved bus. To connect 120 volt single pole breakers
Or 240 volt double pole breaker, basically a two single pole breaker stacked together with both Switch handles tied together. In this panel i am using two single pole breakers at 120 volts each. Now far right is neutral/ Earth bus the Neutral and Earth
Is tied together to ensure that bus is at zero potental also (it served all way back to pole with 14.4 KV transformer Primary Neutral on this too! ). It main job to carry the unballance currents of 120 volt back to transformer. This basically how american homes get 240 volt and 120 volt electric supply on 240 volt meter.