String

String is an item primarily received by killing Spiders, which drop 0-2 units on death. String can also be found (rarely) in dungeon chests, but because dungeons tend to be hard to find, this is not a very good method of obtaining it. As most players use only very limited amounts (five bits are enough to create a single Bow and Fishing Rod), building a special mob trap to harvest it could be considered a waste of time; while large quantities are required in order to craft Wool, that resource is more readily harvested directly from Sheep.

Crafting
String's only use is in crafting. It can be used to make a Bow, some Wool or a Fishing Rod.