Electrical isolation is needed in electrical and electronic circuits to prevent components and people from shock and short circuits. Electrical isolation also helps in supplying power to circuits while keeping them electrically separated. Effective isolation can be realized by using an isolation transformer.
An isolation transformer is used to transfer power from AC to another component or circuit. Therefore, isolation transformers isolate the internal circuit from the mains power for the purpose of keeping people and components safe from errant power spike and erratic power supply.