Edison’s DC [Direct Current] was very expensive then & needed power stations nearby even to cover short area. Also due to higher rate of break downs, they needed frequent repairing.
Tesla’s AC [Alternating Current] was much cheaper & free from the cons or defects of DC.
Popularity of AC over DC was a threat to Edison’s business. Thus at once he tried to demonstrate the danger of AC by putting convicted murderer into dead using AC powered electric chair.
Tesla replied him by demonstrating “The experiment of Tesla coil”. Where he let 250,000V to pass through him while, proving the safety of his invention i.e. AC. [Due to the higher frequency of the Current it only travels on the surface of Tesla’s body]