Season your fish fillet. Heat a frying pan on medium high heat for 3-4 minutes, add a drop of oil and lay your fish on the oil. Cook the fish until the fish is slightly brown along the edges. Turn the fish and cook for an additional two minutes.
Allow pan to become hot. Pour oil or butter into the pan. When the oil or butter gets hot, slide the fish. If they are thin keep it in the heat high. If they are thick, turn it down as low as medium for a steak.
Get a cast-iron skillet or other heavy-bottom pan VERY hot. Drop in a small dash of oil to coat the pan, then drop in prepared fish about 30 second on each side. If pan begins to cool, stop and let it get hot again before adding next fish.
Well searing refers to cooking meat at a very high heat very fast typically using a heavy skillet that was oil that is really hot. You brown each side quickly.