On a side note, Wikipedia is a horrible source to learn a new algorithm.
I can't say for A*, but many other algorithms (like Bayes Probability, FFT) I tried look up made little sense to me on Wikipedia, but learning from some well presented material(be it text, graphics or video) made them easy to comprehend.
I wrote this about 10 years ago and hope to spend some time one day making it simpler, but it seems to have helped a lot of people judging by the emails I get... http://www.heyes-jones.com/astar.html
Not as concise as the explanation given by irahul (which actually made me get the concept), but your article is very interesting and well written, and it is absolutely worth sharing to a couple friends of mine who would probably not get it with the wikipedia article.
I Wikipedia has helped me understand many algorithms. It's probably something like 50% chance I will get it, but the articles so short it's worth a first look.
I can't say for A*, but many other algorithms (like Bayes Probability, FFT) I tried look up made little sense to me on Wikipedia, but learning from some well presented material(be it text, graphics or video) made them easy to comprehend.