Simplify the following text for a Grade 3 native English-speaking person.
Original: In general usage , the term ` steam engine ' can refer to integrated steam plants such as railway steam locomotives and portable engines , or may refer to the machinery alone , as in the beam engine and stationary steam engine . Specialized devices such as steam hammers and steam pile drivers are dependent on steam supplied from a separate boiler .
Simplified: A Steam engine is an engine which uses steam from boiling water to make it go .