The soft tips dart is made for the electronic dart boards, and the tips on these darts are detachable for ease of replacement. They are made to be replaceable as they are made of plastic and can get damaged when in use. Being plastic, they are obviously safer than their steel tip cousins and will not leave holes in the wall when you miss the dartboard, but can still mark the walls so care must be taken and you still need a cabinet or dart backboard.
The introduction of electronic darts has upset some of the "old school" darters, but its popularity cannot be denied. Arachnid one of the pioneers of the electronic game has tournaments around the US using their famous galaxy range of arcade style dartboards and have tournaments in most states. There is even a company in Europe called Cyberdine which has plans to put one of their electronic dart boards in every school in Croatia to teach the kids darts! So the electronic game is here to stay and it will surely dominate the sport before too long.
The tips themselves are very cheap fortunately and are replaced using the dart tool that either come with the dart set usually or can be obtained for $10 or so. Halex has even come up with a notched version of the soft tip, which is supposed to help the dart stay in the dart board. I haven't tried them so I can't vouch for them, but they are worth a try.
Soft tips are usually made with a 2 BA thread, to screw into the barrel of the dart, there are some Inch versions about as well, but stick to the 2BA sort as everyone has those.
The soft tips dart revolution has now transformed the game, and the board manufacturers have been quick to come out with more and more sophisticated electronics to their dart boards adding better displays and more games to produce some truly amazing products, like the Halex Armada board that has a laser throw line and a BristleTech dartboard that can take both steel tip and soft tip darts.
Soft tips darts are getting very popular for the home user especially for their greater safety and sheer novelty value; no scoring necessary and all the game rules are programmed into the board as well so less arguments.