The name steel tip darts has only recently been coined since the advent of the soft tip darts. Previous to the soft tip revolution, all darts were steel tipped and were simply called darts. But now there are two types of dart game, the traditional game played on Bristle dart boards with the old steel tip darts and the new electronic game that uses soft tip darts and electronic dart boards.
As the name suggests the tips of steel tip darts are steel with a sharpened point so they can stick into sisal or paper or even a wooden dart board. The steel tip has had some innovations over the years, like the Bottelsen No Bounce out darts that had the trademark Hammerhead system in the grip whereby the tip can retract slightly into the body of the dart absorbing the sharp impact if a dart hit the wire or staple on the dartboard allowing the forward momentum to push the dart past the obstacle and stick into the board.
Black widow darts had a similar system called a movable point that also had the added advantage of allowing the body of the dart to swivel around the tip achieving the same effect as spinning shafts i.e. if a dart hits the flight of a "widow" dart that is in the dart board, the barrel can rotate so moving the flight and that reduces the deflection of the dart coming into the board.
Another step forward for darts is the metal used to make the darts today. Tungsten has all but taken over as the material of choice for the body of the dart, with its superior density to traditional brass, the same weight of dart can be made much thinner, increasing the chances of getting three in a bed and that 180 score.
Apart from the tip, the body , shaft and flights are the same for both steel and soft tip. The weight of the darts is the other difference. With steel tip darts you can go all the way to 50 gm if you want, whereas soft tip darts have a 20 gm limit normally, to stop the dart damaging the electronics.
As for maintenance of your steel tips, be sure to keep the point sharp, either by rubbing the tip on some grinding paper or using the shaped carborundum stone you can get specifically to keep steel tips sharp. If you want to spend the money, there are motorised sharpeners that will sharpen your dart at just the right point angle.