Crafters are machines that will automatically craft items for you.

Crafter Recipe

Once you've placed down a Crafter, simply sneak+right-click it to open it's GUI. In the GUI menu, there will be a single open slot where you can place the item you wish to craft.
Crafter GUI
After you've placed the item you want to craft in the Crafter's GUI, all you have to do is supply it with the ingredients. You can do this with a hopper or Pipe. Once it has at least twice as many ingredients as it needs (it always stores one set to avoid clogging up), it will craft however many of that item it can and either spit it out like a normal dropper/dispenser or, if there's a container in front of it like a chest or another Crafter, it will insert the crafted item into whatever container is in front of it. You can also place a Pipe in front of it and it will insert the crafted item directly into the Pipe. You can chain multiple Crafters together this way to craft more complicated items. Crafters will play an animation with some particles when they craft something to indicate that they are working.
An example of chaining Crafters together would be having one turning logs into planks, inserting into another Crafter that turns those planks into sticks, and inserting into yet another Crafter to use those sticks to craft a pickaxe. The last Crafter in this example would also need to be supplied with the other pickaxe ingredient, like diamonds for a diamond pickaxe. You can use setups like this to keep other machines stocked, like feeding pickaxes, hammers, or axes into a Miner.

As mentioned above, the Crafter will keep at least one of every item inside its inventory. This means that, even if you have enough materials to craft one item, it won't craft that item until it has at least two of every required material. This is to prevent the Crafter's inventory from clogging up with one material, leaving no room for other materials the recipe requires.

The Crafter can be used to craft PandaCraft-specific items, such as HammersCrooks, and even other machines.