Pre Processing… names the files to be executed before the model is simulated. These might dataset conversion commends or some other actions to ready the model for simulations. You can specify multiple files in a comma separated list.
Post Processing… names the files to be executed after the model is simulated. These might can be commands to manipulate or export results or .vdo files to write results to a database.
NOTE When a model is simulated from a Venapp or command file, or when using the Vensim DLL the pre and post processing settings are not used. If you want to do something before or after a simulation you should put those actions directly into your script (possibly using the SPECIAL>RUNCOMMAND command).