Makers can be used to turn raw materials into processed items. You automatically learn crafting recipes for makers as you level up your different skills.
How to Get Makers
To get makers, you need to level up your skills. You will automatically learn the crafting recipes for different makers when you level up the skills related to those makers.
You can also get some makers as Title Rewards from the Town Hall, if you check the Title Rewards area to the right of the Requests Board there.
Some of Lovett's Gourmet Requests will reward makers, as well. The list of requests is in the front room of Lovett's mansion.
How to Use Makers
Once you get a maker, you can place it outside on your farm. It needs to be placed in a 2x2 square area.
After placing it, you can check on it, and you will be asked to choose what to put into the maker. See below for the list of items you can put into each type of maker. Makers take a certain amount of in-game time to create the finished product, so be sure to check on the maker later to get the new items.
You can't process multiple items at a time, so you should try to create multiple makers of the same type to be able to make more things at the same time. (This is scheduled to be changed to allow processing multiple items at a time in version 1.0.5.)
For a list of all makers, the materials they require, and the products they create, see the List of Makers and Products page.