Cubed steak, aka. "Minute Steak", is a cut of meat that has gone through a mechanical tenderizer which yields the distinctive cube-shaped design on the surface. It's wonderfully versatile because it's excellent both for preparing in just a little time--hence, its nickname, "minute steak"--via sauteing or pan-frying, or braising as in a long, slow oven or Crock-pot recipe.
Cube steak does not contain much fat or marbling, so the leanness makes it great for meal options such as Country-Fried Steaks or stews. Another consequence of leanness is that it can dry out quickly, so it's best to use cube steak in recipes that will yield gravies or prepared with moisture-rich sides like mushrooms and onions.
Cooking tip: To keep cube steak tender and not chewy, allow plenty of space between steaks in the pan!