Unlike pork, beef does not have to be cooked until it is well-done. Steak can be served with different amounts of cooking time. The six classifications for steak are blue rare, rare, medium rare, medium, medium well and well-done.
Blue rare is cooked on the outside and completely red on the inside. Rare is cooked on the outside and about 75% red on the inside. Medium rare is cooked more so that it is about 50% red on the inside. Medium is about 25% pink on the inside. A medium well steak has a little bit of pink on the inside and a well-done steak is cooked until it is 100% brown.
Chefs use their knowledge of how the steak looks and how it feels to determine when it is ready. A well-done steak is much harder than a blue rare one. Obviously a blue rare steak needs the least amount of cooking time.