Understanding Heat & Work: An Engine Explained

[influx]

My book states:

''An engine is a device that turns heat energy into work''

I know the definitions of both heat and work (heat is the energy transferred by virtue of a temperature difference and work is the energy transferred when a force acts through a distance) but I'm struggling to understand the above. Could anyone elaborate on the above?

Thanks

 

[WannabeNewton]

What exactly about the statement is confusing you?

 

[influx]

What exactly about the statement is confusing you?

How is this done? I mean both are forms of energy? So how is heat converted to work?

 

[dauto]

In practice it is done like that: Heat warms up a gas that expands producing work on a piston.