USDA Grades for beef sold at retail level are Prime, Choice, and Select. These grades are mostly obtained by the age of the animal, and the amount of marbling. Marbling is the intramuscular fat found within the cuts of beef. Marbling is associated with flavor and overall quality.

USDA Prime Beef: beef from a young animal, typically 18-24 months, that will be tender, flavorful, and will have Moderately Abundant Marbling (Above left) or Slightly Abundant Marbling (Above Right). These are the official pictures, or shields, used by the USDA to grade beef. Prime Beef is typically sold in high end restaurants, hotels, and grocery stores.

USDA Choice Beef: beef from a young animal, typically 18-24 months, that will also be tender and flavorful, with slightly less marbling than Prime. Choice Beef will have Moderate Marbling (Above left), Modest Marbling (Above Middle), or Small Marbling (Above Right). These are the official pictures, or shields, used by the USDA to grade beef. USDA Choice is what is often sold in grocery stores and is usually prepared in the large chain steak restaurants.

USDA Select Beef: Has Slight Marbling as pictured above. These are the official pictures, or shields, used by the USDA to grade beef. Select beef is leaner than the higher grades of beef and is also consistent in quality between cuts. Because there is less marbling, the Select grade typically lacks some of the flavor associated with the higher grades. Select Beef is the cheaper option often sold in the grocery stores.
https://www.ams.usda.gov/grades-standards/beef/shields-and-marbling-pictures

The USDA also grade tenderness by performing a slice shear force test. Beef can be graded Certified Tender or Certified Very Tender.

https://www.ars.usda.gov/ARSUserFiles/30400510/protocols/SSFProtocolforsmallvolume.pdf
https://www.ars.usda.gov/ARSUserFiles/30400510/protocols/SSFProtocolforlargevolume.pdf