What is YAGNI?

This is generally a software engineering term that stands You Ain't Gonna Need It.

Basically in software development a programmer should never create a "generalize" module for the sake of generalization, adding complexity to things that will probable never exist. This usually happens when a programmer over thinks too much about code reuse should be advocated in every modules he will create.

A best advice usually given is keeping all modules in the simplest state as possible. And adding new features as needed so that modules might not lead to code bloat.