Hey there,
Centripetal force and the gravitational force are actually two entirely different forces. The use of the term centripetal force is somewhat misleading. It is not a 'special' force like the force of gravity (one of the four fundamental forces of nature). The term centripetal force is a categorization of the unbalanced force acting on an object while it is in circular motion (Centripetal Force has its origin which means 'center-seeking' force). For example, think of these visual examples: (1) swinging a yo-yo over your head, (2) you in a gravitron ride at a theme park (the one that spins you around in a circle very fast. Also usu. the one where most people get sick!), (3) a fighter jet pulling a loop in the air. Let's take a look at all three cases here. Firstly, in order to understand centripetal force, you must understand that ALL objects have a natural tendency to EITHER be at rest or move in a STRAIGHT line at a constant rate. A property known as inertia (resistance to change). So to keep an object in circular motion one must apply a constant force always directed towards the center of the circle that the object is traveling around.
Now (1) the obect we were dealing with was the yo-yo. In this case, if we let go of the string, the yo-yo would have flew off in a straight line. However, it didn't! Why? Because the string was constantly pulling it at every moment. Thus the unbalanced force in this case, which we can categorize as the centripetal force, is the tension in the string. (2) The object in this case is you. In this case the walls are acting to keep you moving in a circle. If they weren't there, you would not continue moving in a circle. Thus the force that the wall exerts is considered the 'centripetal force'. (3) Fighter jet is the object. The force that the air pressure exerts on the jet is the unbalanced force keeping the jet in circular motion and thus the 'centripetal force'.
Now, why do we hear all the time esp. on TV terms like, g-force, etc? This is because we tend to use the acceleration due to gravity (9.8m/s^2) as a 'baseline' with which we can compare other things in nature that are accelerating. For example, a fighter jet pulling a loop experiences a tremendous acceleration while moving in this circular path. To compare this acceleration, we compare it with something we know. Namely, the acceleration due to gravity. So when we say a fighter pilot pulled 5g's he accelerated at a rate 5 times that of gravity on earth.
One can also 'simulate' gravity on Earth in a gravity free environment. The easiest way to do this is to have something accelerate you! Moving in a circular path is accelerated motion. Where the acceleration is directed always towards the center. Your 'feeling' of weight is a result of the ground pushing up on you on Earth. If the ground was not there to push up on (or the scale pushing up on you!) you would feel weightless. Imagine a car tire that had a diameter of a high rise building that is in empty space somewhere. If you could be placed inside this tire and the tire rotated at a high rate of speed, you would feel the walls of the tire always pushing on you directed towards the center (centripetal force in this case). Your body's inertia wants to keep you in a straight line, but the walls of the tire are preventing you from doing so. This effect, the constant pushing force of the walls of the tire countering your body's inertia, provides this 'feeling' of simulated gravity. One can simulate your weight if you knew the radius of the tire and had the ability to change the rotational speed of the tire.
Hope this helped. I am a physics teacher in New Jersey. Happened to stumble on this message. I had a link for you to check out, but it is dead at the moment. When it is up, I can send it to you.