Basketball rules question: charging vs. blocking?

I don't really watch basketball, so on the occasions that I do, I often cannot spot certain fouls the way they are called. Blocking and charging, for example, I cannot tell apart.

Can someone please explain the difference to me, and what's the penalty if someone gets called for either one? And please explain it as you would to someone who does not play or watch basketball. I grasp the basic rules of B-Ball, but the intricacies of fouls is hard for me to grasp. A lot of times, I see a foul that is described as "flagrant" and results in an ejection, but to me, it didn't look that bad. There seem to be a few fouls in B-Ball that just seem to be called so the refs can get some TV time. I see fouls called where the announcers are agreeing with the call, but I cannot see what the player did wrong. This is usually the case with charging or blocking. Whenever blocking is called, it almost always looks like charging to me, and vice versa. What do I look for to tell the difference? Or are the NBA refs just that bad (as I've heard players complain) that someone like me who doesn't even watch the game can get calls correct that they are getting wrong?

If you could provide a youtube link to an example of basic charging and another for basic blocking, that'd be awesome. And thanks in advance.