Shechitah is the slaughtering of animals for food in the ways as laid down by the Torah. It is imperative that the animal feels no pain during the process, and is not alarmed in any way. The actual process is performed by a Shochet, a man who trains for a number of years. The shochet takes a knife that has been sharpened since the last time it was used, and cuts the animal's jugular vein, and the others surrounding it which carry the pain. The shochet is trained to do this with such speed and accuracy that the animal does not register pain. It is allowed to bleed (without it knowing anything is going on) - until the point it feels tired and then dies.
The animal is then checked for disease, and any diseased parts are immediately discarded.