Rod "action" and "power," which I've introduced briefly, are the key parts of understanding your rod. As I've said, if you don't understand these two terms, that doesn't mean you won't catch fish. I'm explaining for those who do want to understand, and for those who want to take the time to learn so they can catch more and better fish.
Action (http://www.vingle.net/posts/336742-Choosing-a-Rod-Rod-Action-Basics) is basically where your rod bends, and how much it bends. This might be slow, fast, moderate, etc. See that card for more details.
While Action is how much a rod bends, power is how much it resists such bending. Even if a rod flexes, there's going to be resistance. We use "power" to describe that resistance. Powers range from Ultra-Light to Heavy. This video explains more about fishing rod power, and is also a great review about action and how they work together.
Action is arguably more critical than Power when looking at different fishing techniques, but both are important. One big problem with understanding these terms is that there is now standard: so, one rod at fast action, medium power isn't going to feel like fast action, medium power rod from another brand. Annoying, I know.
Power is the backbone of being able to really set a hook, so if you have a specific lure presentation you like to fish, or if you find your rod not bending enough to set a hook that might be bit at awkwardly, you might want a rod with less power---this will lessen the resistance, and the hook set will come easier.
Realistically, each lure presentation works best with a different rod power and action, so if you're really interested in making sure you match those, you're going to want to return to the questions of what you want to fish, and what you want to fish it with lure-wise.
And so, next time, I'll talk about pairing lures and rods.