I suspect any developer reading this is aware of the DRY principle because it is just so ubiquitous. If not though, you just need to know that it stands for "Don't Repeat Yourself" and is generally invoked when advising people to not copy and paste snippets of code all over the place and instead consolidate logic into a central place.
DRY was the first programming principle I encountered and probably the only one I was aware of for the first year that I was a developer. It's also probably one of the simplest principles to understand. If you see two things in your code that are the same, maybe they should just be one thing. Hard to argue with that. But, I think that DRY is just like every other principle out there - it has its place, but it's best taken in moderation. And I think that, due to its ubiquity and simplicity, we tend to take DRY too far, far too often.
Source: Why DRY is the most over-rated programming principle, an article by Gordon Cassie.