Esquire has this guide to steak, including different aging techniques, types of beef, grades and cooking:

Everything You Need to Know About Steak

These videos can help you learn a little more:

If you want to learn more about beef grading, this video will get you started: Beef Grading

The standard grading scheme in the US has Prime, Choice and Select (along with 4 lower grades, bottoming out at “Canning” grade), with only 3% of cows becoming Prime beef. But connoisseurs have their own scale that goes far beyond Prime. In this rarefied world of super-steak, you can find meat that costs $30 per ounce:

The description on the video is interesting:

Wagyu beef’s quality is determined differently: by a 12-point marbling-score scale.

Using the scale of Wagyu marbling scores, USDA prime would have an equivalent ranking of 5 to 6.

The most prized beef in Kobe, Japan, would rank the equivalent of a 12. The marbling is so dense that the lean muscle to marbling ratio can reach 9:1, or 90% fat to 10% meat.

This Kobe is unbelievably rich … too rich for many palates. Some say it looks like a piece of meat that has been left in a snowstorm … fine strands of lean meat embedded in pure fat.