The steam engine turned heat into controlled mechanical work on an industrial scale. That sounds technical, but its real significance was civilizational: mines could be drained, factories could run independent of rivers, and locomotives could move goods and people at unprecedented speed.

Steam power compressed distance and time. It helped create the industrial city, national rail networks, and mass manufacturing. Once societies learned to harness fossil energy through machines, economic growth accelerated into a new gear.

Reference:

Wikipedia: Steam engine

https://en.wikipedia.org/wiki/Steam_engine