I often read in recipes that I should "rest" meat after it has been cooked but what does resting the meat actually do?
There are a couple of reasons why 'resting' meat is a good idea. First, as the meat cooks the muscle fibres contract, which forces the juices out. Letting the meat rest helps the muscle fibres relax so the juices are re-incorporated into the meat and not lost on the chopping board, which would happen if carved immediately.
The second reason to let meat rest is to provide an evenness. Basically as the meat rests it continues to cook slightly and it allows the meat to gain an overall 'doneness'
Also keep in mind that meat continues to cook once you remove it from the heat source. The resting period allows the cooking process to complete.
Pulse is so correct that it is so important to let a piece of meat rest. It is so evident when a steak is cooked placed straight on a plate and cut into , all blood that hasn't been able to settle back through the meat will be pooling on the plate in seconds and you are left with a dry overbooked piece of meat. In large joints of meat I have found that a short resting time creates the meat to be tougher to cut through and again a loss of crucial juices then a rested piece. Creates the question with many cooks is a slightly cooled piece of meat rested and relaxed better than a nice hot piece of meat off the grill or out of the oven - I Believe Yes.