You’ll need to learn some quantum theory to really understand transistor since field effect can’t really be explained using other analogies.

Basically because there is water at a high height (high voltage), the height in another pipe changes: Without the water actually flowing through the pipe.

Transistor let you set voltages without passing current through (in the real world, there is current and thus heat being generated as waste, but it’s extremely small compared to the number of switching components there are).