Donuts. Bowling balls. Tires. What do these things have in common? They’re all round and they all have holes. Sometimes holes serve a purpose. But when it comes to software, holes—or gaps—are not good. 

A simple but significant difference between “customizable and configurable” software solutions is that configuration requires no changes to the source code; this one distinction has powerful business ramifications that have driven many companies to move far away from customizable tool kits.