To make life easier for people who are confused about all the terms and different grading systems out there I took the effort of placing them next to each other in a digestable format. Note that this is not an exact match as these systmes were not made to be exactly translateable to each other, but it works about right in most cases.
Grading coins correctly is one of the most important aspects of determining a coins value. To be successful in buying coins that do well in terms of their value over time it is imperative to grade coins correctly and to understand the different grading scales that exist in the world.
Anyone just starting out buying coins will ask themselves - What does all these numismatic abbreviations such as VF, EF, UNC or worse gVF/aEF, aVF-VF, etc. stand for?
As with everything, something starts simple, then by attempting to become more precise and accurate, it becomes more complex and hard to understand for someone starting out. It is the same in the numismatic world.
The basic principle around grading is simple and around wear, which increases the longer a coin is in circulation. Starting from "Uncirculated" in condition for a coin that hasn't had the hard treatment of hand-to-hand and in trade circulation, it deteriorates through "Extremely fine" to suggest a still very nice coin, to "Very fine" for a decent example, to just "Fine" for still an ok example, to "Very good" and "Good" to actually quite poor specimens, down to the ultimate recognition of a "Poor" coin that looks almost like a blank piece of metal, worn flat by decades of circulation.
Looking at some of the longest circulating coinages, such as Victorian pennies and other lower value denominations of long-reigning monarchs, it is clear that coins can be used for a very long time, sometimes up to 50 years. But from the moment a struck coin is catapulted out of the minting press it is exposed to a number processes that each leave their marks when thousands of coins are put in bags to be distributed to banks and finally into circulation.
What further complicates things is that there are more than one grading system. Actually there are about as many grading systems as there are countries! Most of the European countries use the same scale but apply their own names to each tier. But recently CGS, UK's first professional grading agency, has made a scale of their own.