A Properties file in Java is a list of key-value pairs that can be
parsed by java.util.Properties class.
Generally a Properties file has extension .properties e.g.
myapp.properties.
Properties files are used for many purposes in all kinds of Java
applications. Some of the uses are to store configuration, initial
data, application options etc.
When we change the value of a key in a properties file, there is no
need to recompile the Java application. So it provides benefit of
changing values at runtime.
https://www.ibm.com/docs/en/sim/6.0.0?topic=files-properties