May I suggest that you word your requests a little more politely, e.g. "Please explain... Thank you."
A flat file is just something like a text file, where there is data but there are no specific relationships between any of that data except what you impose on it from outside. The altrenative is a relational database where there are specific relationships between the various tables of data that inherently allow you to view and retrieve data in various useful ways and also maintain the integrity of the data.