The "skeleton" is just something artists use to sketch out the figure, and get an idea of where they want things to be. I, myself us simple, soft shapes instead. I find this to be alot easier, and alot quicker overall.
Kojas, it's important to think in 3D. When you see the world, what is happening is that 3D objects are being projected into a 2D image onto your retina, after which your brain reconstructs the 3D objects.
When you draw, you imagine the 3D objects, and you draw their projection onto the plane of your picture as if you were looking at them from some particular point of view. The viewer's brain then reconstructs the 3D objects from the drawing as if it was reconstructing a real scene that it was looking at.
Drawing a skeleton helps you think about the shapes of the 3D objects and then helps you work out what their 2D projection will be from your chosen viewpoint.
As Vineris suggested, practice drawing simple 3D shapes like cylinders and boxes from different points of view. Once you are comfortable with that, then all you need to do is realize that skeletons are the axes (or centre lines) of the cylinders and other shapes that make up the object you are drawing.
You may have to start with more basic basics before you can begin thinking of things like volume and depth. This site, created by a Simpsons storyboard artist breaks everything down in very clear articles starting from level 0: [link]
Its for...everything. Proportion, movement, pose, etc. You NEED that to place your figure correctly. The people who don't use it and are GOOD (most people who think they don't need it aren't) do it in their heads.
If your drawings are still off, you're not using the right proportions on your skeleton.
Cheaters Guide to 'real' Proportions:
Torso (shoulders to crotch) about 2-2 1/2 heads tall Shoulders- at least 2 heads wide Upper leg: same as measure from crotch to shoulder Lower leg to bottom of foot (heel): same as upper leg Upper arm (elbow to shoulder): from shoulder to navel Lower arm to wrist: same as upper arm Hand (from palm to end of middle finger) about from chin to hairline BUT hands are funky and you can play with this one. Foot: 1 1/2-2 hands long (again you can play with this)
Breaking complex 3D shapes down into more simple ones helps you think 3-dimensionally. (The key word here is 3D. Spheres and cubes and cylinders, not circles and rectangles.) It makes it easier for you to apply perspective and lighting to a complex figure. It makes it easier to turn that figure around in your head so you can draw it from a different angle. Guidelines help you remember where to put details.
If you're having trouble with things like hands, start with easier shapes until you get what you should be doing. Things like cups, fruit and simple toys are easy to find and easy to practice on. Draw them from life, it's often useful to be able to turn the item around and draw it from a different angle. Later on you can use this same method with human bodies, animals, cars, street scenes, whatever complicated thing you want to be able to draw.
I'll generally use an egg shape for the basic proportions on the hand. With the fingers roughly crossing and then add a thumb sticking out to the side. Depending upon what sort of picture you're drawing, that should give you the basic hand shape, as far as the fingers go.
(Slightly OT, but the reason why cartoons typically only have 4 fingers, is that it's a lot harder to add them while still having enough room to tell them apart)
Check out some Loomis books, he does a great job of explaining the basic 'fleshing out' process of starting with the basic forms and masses and moving on to the specific shapes. I believe they're out of print, so this link should be alright (PDF downloads) [link]
Some of it is advanced, but Fun With a Pencil should get you thinking in terms of 3d forms (volume) instead of worrying about copying 2d shapes (contours).
I use the basic shapes for proportions and to lay out the pose I'm trying to draw. The basic shapes really help with perspective to. It's much easier to make adjustments to those things when you only have the very basic shapes rather than something that's already detailed.
When you're just starting off with learning the skeleton don't worry about learning exactly how it looks, as long as you have the basic shapes of the bones you're good.
Look up the block figure as well. It will explain how the basic shape method works.