Crafts can be used on residents or structures to increase their yield, price, both, or neither. Creating / upgrading a craft gives a permanent boost to your town's total yield.
New crafts can be discovered when an artisan (Resident whose current job is an artisan) visits a Wholesaler or Wholesaler(L) structure. There's a 33% chance that a new craft will be unlocked when an artisan visits the structures.
Requirements of unlocking new crafts can be a combination of several things such as structures built in the perimeter of the Wholesaler (both version) structures, the current total amount of research points, and/or the stats of the visiting artisan.
For requirements that needs structures built, the required structures must be built inside a 5x5 square area that are centered on the Wholesaler.
Only one new craft can be unlocked for each artisans' visit to the Wholesalers. The order of which craft that will be unlocked is determined by its position in the list at the below table. Crafts that are listed high in the list will get higher priority to be unlocked than crafts listed below in the list.
So if Elekiter and Bokken meets the requirements to be unlocked, Elekiter will be unlocked because it's placed higher than Bokken in the list.