"Saute" (saw-tay) is a cooking method to cook quickly over high heat in a small amount of fat (oil, butter, etc.).
You can use a skillet or a special saute pan, but make sure it is big enough to allow food to sear, breathe, and give off liquid during the process. Proper browning requires the quick evaporation of moisture, particularly water. Be sure to preheat it -- you need high heat when sauteing to cook ingredients quickly. Otherwise, the moisture will come out of whatever you are cooking and it will not brown.