skeletor6

I'll help you out here Joe and also confuse you at the same time. 
 
First off, there are no absolutes when it comes to actions and what they actually mean. Manufacturer's assign ratings at will and they will vary from rod series to series and across brands. In general, here is what a rods action chart will look like....
 

 
So, as you see it is the degree of deflection from a line parallel to the rod blank. In general, a slower action rod will have more of a parabolic type of look to it when it is under load. The tip will flex further down into the rods backbone. An extra fast rod will get into the rods backbone much quicker.
In a generic situation, you can think of it as an XF action as having a stiffer tip and the action will get into the backbone of the rod much more quickly. The tip will have less give to it in most situations. Contrarily, a slower action rod, such as a moderate, will bend much further down into the backbone and the tip section will be softer. This is good for crankbaits as it will not overpower and rip the bait from the fishes mouth. 
 
Now see these general statements do not hold true in all situations. A great example is in a designed dropshot rod. Manufacturers may make the tip section of the rod extremely soft and giving while having a stronger backbone, thus the action may look more like an XF or F or whatever someone decides it to be, but yet not have a stiff tip at all. My shimano cumara dropshot rod is good for that CUSDX72M. It is rated as having an XF action, but it is quite soft in the tip. Contrarily, you can pick up a St. Croix and there extra fast actions are usually very stiff.
 
Another general feature I have noticed is that XF actions both get into the backbone quicker and get out of the backbone quicker. Sort of like a bungee effect, some users who are looking for some serious power will like to use a slower action tip because once that rod flexes down lower into the backbone it will stay pinned there and allow one to haul a fish out. I like to think that XF tips usually use involve the tip-section more as the power of the rod since it does not flex so deep into the blank. Whereas, the slower action rods involve more of the blank as its power source since it bends down further into it.
 
What I am trying to do is just give you as many different examples or different ways to look at it so maybe you can get some kind of an idea about what is going on. What is tough is there is such a large variance among manufacturers and there interpretations. I like to thoroughly examine the tip section of my rod and add some weight and pull down and see how the rod bends and notice its properties and the degree of deflection that it has. Also, I like to see how much force it actually takes to get the tip of the rod to move to figure out the stiffness of the tip. Then I decide if the action of the rod is something that I find desirable for the technique that I am going to use.
 
Others may have different interpretations about what these mean to them and have different properties they look for in a rod. I really feel the action of a rod is so crucial to how that rod is going to fish. Really it is an art-form in some aspect, some actions just feel right and are very responsive to what you are looking to do. Good example for me is the GLX BSR852 vs the NRX 852s....they are rated the same, but the action on the GLX version just feels "special".