While Warren Buffett has never explicitly said that he's a GARPer, he may have very well have invented it. Buffett started out as a die hard value investor, strictly buying stocks that were incredibly cheap based off of their balance sheet. His philosophy slowly changed to more growth oriented companies, but as always he wasn't willing to over pay for them.
Let me explain the difference among these using real estate since that's a lot easier for people to value. Value investing is only willing to buy a house for a lot less than its replacement cost. You see a house and it's selling for say 50% of what it would cost if you had to build a new one, that's value! The problem is that it may be that cheap for a reason. Like for instance it's in a bad neighborhood and you can't rent it out for anything. No cash flow.
Growth on the other hand is buying something that is overvalued and hoping that rent pays for it eventually because the rental rates are growing very quickly. You buy an investment property where cash flow from rent isn't enough to cover the monthly costs of the house. But you're hoping that the prodigious increases in rental rates will eventually cover this gap and the property will be worth much more later. Here's the problem. The growth may not come and you're stuck with an investment that is losing money each month. Just ask all of the investors who bought real estate using this method over the past 7 years.
Now here's the beauty of GARP. You buy a piece of real estate that you know can be rented out for X dollars. After doing your cash flow analysis you see that this will be less than (with a nice margin of safety) your projected rent. Thus creating a situation where it's making you money and you're not hoping that something has to change. Even during the worst of the property bubble, rental rates only dropped about 10%. If you had a nice cushion you would have been fine through out the whole bubble.
Finally, and most importantly, if you can't find any investment meeting GARP standards, don't buy into that market! It's a good sign of a price bubble.