Yeah, you can just keep your 14-day trial CD key and keep on playing, but I believe the 14-day trial is just the basic game and does not include Catacombs or Darkness Rising. Those are an additonal $20 to buy and you will need to purchase those to upgrade the game. The graphics are so much better after you buy those.
For the original question, salvaging turns almost any weapon or armor piece into base raw materials.
Lets say you are a caster and you get a bow drop. This bow has no value to you and you go to a merchant and see how much you can sell it for. The merchant says like 1gold for it, which is not much. If your caster is a tailor, with woodworking (need woodworking to salvage bows), you can hit your salvage button and make the bow into 26 boards (type of board depends on level of bow)...but that 1gold would probably now be 15gold to the merchant if you sold back the 26 boards.
There is another thing you can do which will increase the value even more and that is trinket the 26 boards into things that sell for even more money. This used to be one of the main, if not the main way of making money in this game...People would go to Darkness Falls and farm seals, which are used to buy weapons and armor..they would then salvage these weapons and armor into metal and trinket them into hinges which can yield you decent cash (maybe 500gold to near a plat an hour if you are good at it).