Durability is a concept in the game which is applied to tools where after a certain number of uses (depending on the specific tool) it will eventually wear out and break. The durability number or amount represents the number of times that the tool can be used before it breaks and can't be used any more.
There are three broad classes of tools in the game, to which durability matters:
Each successful tier of tools has more uses, but at the cost of more resources and more complexity in terms of more steps that are required to make that tool including more buildings that must be constructed in order to make that tool.
Crude Basket • Besom Broom • Fishing Rod • Knitting Needles • Shears