The boiler uses highly purified water in enclosed tubes and boils it to make steam.
To do this, ground coal is blown into the bottom of the boiler and ignited, creating a fireball.
The intense heat from this fireball causes the water running through the tubes in the boiler to turn into steam, which is collected in a steam drum at the top of the boiler.
The steam is then passed through another set of tubes in the boiler where it is superheated to extremely high temperatures.
This high pressure, high temperature steam is then piped to the turbine.