What does separable lean & fat and separable lean only mean?

https://i.imgur.com/BqYl8iU.png

Two different entries I found...

Beef, Top Sirloin, Steak, Separable Lean and Fat, Trimmed to 1/8" Fat, Choice, Raw
Beef, Top Sirloin, Steak, Separable Lean Only, Trimmed to 1/8" Fat, Choice, Raw

What are the differences and which entry do I use if I'm buying steaks from supermarket?

Answers