I've only done 'passive' things with IWP, just reading information from a database. Never had people entering data from a web browser until now.

At exactly what point does user input become part of the database?

IOW, if you're working in FMP directly (not via IWP) and you enter data, it's pretty much instantly part of the database. If someone is on a web-enabled version of that page, does it work similarly? Is there a timeout or some other 'automatic' entering of the data?

Basically I need to set up a system where a user can enter specific data (name, department, comments, etc) but I don't want that data to become part of the database until the user clicks a SUBMIT button. If the user enters data and then closes the browser window (without clicking SUBMIT), or if the user enters data and then walks away (leaving the browser window open for potentially hours at a time), I don't want that data to be entered into the database.

The data entered via IWP only 'hits' the database when the submit function is performed.

So it should work as you desire.