What an awesome question. After getting my Medical Rec. I soon got bored of just smoking all the buds there were. So I decided just like you to go into hashes and concentrates. Here is the best explanation I can give:
Full Melt - Some clubs will fool you by saying their hash is full melt, when in fact it is bubble hash. Bubble Hash is the lowest form of hash, but still gets you stoney. Full Melt is a level above and when you light a FM Hash it will evaporate quickly similar to Hash Oils/Puttys/etc. A good full melt will probably be in the 30-50/g range.
Bubble Hash - Just your basic hash. When you light it it lights the hash but the hash does not fully melt. The taste is unique and you can usually find some good bubble hash in the 5-20/range.
Putty - Putty is a form of honey hash that is extremely pliable and is also pretty rare to find. A good putty will have a THC level somewhere between 60-80% and just a dab will have you feeling lifted. Putty is expensive and usually will set one back around 40-60/g.
Flake - I am assuming it is similar to Gold Dust or a full melt kief. Usually created using a CO2 extraction method and usually contains a THC level somewhere between 50-70%. Can some in different colors and is often kept in the fridge to preserve.
Rocks - Rocks can be two different things. 1) It can be a form of hash oil just a little more pliable (like putty), but the hash looks like its been crossed with oil. 2) A form of Hashish that has already been granulated into a rock form. I have seen Hash Rocks in the 30-40/g range.
Kief - The trichromes that fall off the plant. I personally only like to use Kief when vaporizing, but there are some higher quality kiefs out there that can be nice to sprinkle on a bowl. Usually somewhere in the 10-25/g range. Never pay higher than 25/g for kief!
Budder - Have yet to try this type of magnificent concentrate, but if you can get your hands on some buy it. It's not cheap, but I have heard it's the best in the world. Usually has a THC content of no less than 60% and have seen some as high as 88%THC!!!!!! Usually available in the 40-60/g range.
Hash Oil - My personal favorite. Hash Oil is a liquid form of THC and is usually made with an alcohol base. Since THC becomes it's most concentrates in oil form, the THC levels can usually be pretty high for oils, without the price being out of reach. I have found hash oils for as little as 20/g and as high as 50/g, all with the same potency.
How to Apply Hash Oil - This question is a good one. I had it when I first used hash oil and it turned me off from buying it for awhile. What I like to use is 2 different methods:
1) Use a paper clip and swab it around the hash oil jar. When you are content with the amount on the clip you take two small buds and make a sandwich with the oil and the two buds. Pull the buds and the oil will stick.
2) Use a paper clip and swab it around the hash oil jar. When you have enough grind up some herb and throw it in a little hash holder that you have used previously. Put some grinded herb in the hash holder then use the swab and pick up the grinded herb with the hash oil! Make sure to pack some grinded herb in your bong or piece before and then use the sandwich method with the grinded up herb! It's simply the best!
Hope this helps, and remember if you have the money, nothing smokes concentrates better than a vapor globe or a skillet:)