As you develop more sophisticated modules and packages, you will often find that your code needs to be configured in some way before it can be used. For example, imagine that you're writing a package that uses a database. To do this, your package needs to know which database engine to use, the name of the database, and the username and password to use to access that database.
You could hardwire this information into your program's source code, but doing this is a very bad idea, for two reasons:
Different computers and different operating systems will use different database setups. Since the information used to access the database will vary from one computer to another, anyone wanting to use your package would have to edit the source code directly to enter the correct database details before the package can be run.
The username and password used to access a database is highly sensitive information. If you share your package with other people, or even just store a copy of...