A Stick is an extremely useful (and easily crafted) item used in many crafting recipes. The main purpose of the stick is to make tools, but it can be used to make other items as well, such as a Fence or Sign. Sticks are very valuable, as they are used to craft most tools, weapons, utilities, etc. To craft, place 2 Wood Planks over in any crafting grid.
Uses
Sticks are used primarily as the handles for tools, torches, and weapons. They can also be used as the shaft of arrows, the post for signs, or the ties of rails. Sticks are the only building material required to craft a ladder. Sticks are also used to smelt items, albeit inefficiently since they smelt half an item, whereas planks smelt 1 1/2.
Note: The type of wood planks used in the Crafting Table to make fences and Fence Gates will change in color according to the variant of the wood used.
This means that different types of wood cannot be mixed.
Sticks are also used as the handle of most tools and weapons.
Trivia
Some people say that sticks are the most important item in Minecraft, as they are used to craft a large amount of essential items, whereas others believe wood is the most important, because without wood, there couldn't be sticks.
In an early 1.13 snapshot, an item called the "Debug Stick" was implemented and then removed. With this item players could mess around with block NBT tags.