There are several means to generate electricity , like for example we have :
Electricity generated from renewable resources like water , wind and on the other hand from non - renewable resources like coal , natural gas and most fossil fuels.
We have powerplants which generate electricity from above mentioned resources.
Largest power plant in the world is in China : The Three Gorges Dam on the Yangtze River , which produces annually 98.8 (2014) TWh power.
These generated power has to be supplied at various locations , a transformer is used to step up the voltage and transmitted using transmission lines.Before electricity is supplied to the end customer or household the electricity is stepped down from a sub station.
Pictorial representation is shown below :