One of the main purpose of the parameterized graphs is that if we need to run the same graph for n number of times for different files, we set up the graph parameters like $INPUT_FILE, $OUTPUT_FILE etc and we supply the values for these in the Edit>parameters.These parameters are substituted during the run time. we can set different types of parameters like positional, keyword, local etc.

The idea here is, instead of maintaining different versions of the same graph, we can maintain one version for different files.

hope this helps.