Can you explain what you mean "it's just a database". Does Organizer, when it is importing files simply point to the file the content is in and use that information OR does it create a new database therefore using more storage space?
A database is a collection of tables containing data. One way to think of the tables is as an Excel spreadsheet. When you "import" your photos into the database, their physical locations on your drive(s) is recorded in one of the spreadsheet cells.