There are several different types of pattern for different things:
- Crafting Patterns encode recipes made by a crafting table. They can be put directly in a Molecular Assembler to make it craft the result whenever given the ingredients, but their main use is in a ME Pattern Provider next to a molecular assembler. Pattern providers have special behavior in this case, and will send the relevant pattern along with the ingredients to adjacent assemblers. Since assemblers auto-eject the results of crafts to adjacent inventories, an assembler on a pattern provider is all that is needed to automate crafting patterns.
- Smithing Table Patterns are very similar to crafting patterns, but they encode smithing table recipes. They are also automated by a pattern provider and molecular assembler, and function in the exact same way. In fact, crafting, smithing, and stonecutting patterns can be used in the same setup.
- Stonecutting Patterns are very similar to crafting patterns, but they encode stonecutter recipes. They are also automated by a pattern provider and molecular assembler, and function in the exact same way. In fact, crafting, smithing, and stonecutting patterns can be used in the same setup.
- Processing Patterns are where a lot of flexibility in autocrafting comes from. They are the most generalized type, simply saying "if a pattern provider pushes these ingredients to adjacent inventories, the ME system will recieve these items at some point in the near or distant future". They are how you will autocraft with almost any modded machine, or furnaces and the like. Because they are so general in use and do not care what happens between pushing ingredients and receiving the result, you can do some really funky stuff, like inputting the ingredients into an entire complex factory production chain which will sort out stuff, take in other ingredients from infinitely-producing farms, print the entirety of the Bee Movie script, the ME system does not care as long as it gets the result the pattern specifies. In fact, it doesn't even care if the ingredients are in any way related to the result. You could tell it "1 cherry wood planks = 1 nether star" and have your wither farm kill a wither upon receiving a cherry wood planks and it would work.
Multiple ME Pattern Providers with identical patterns are supported and work in parallel. Additionally, you can have a pattern say, for example, 8 cobblestone = 8 stone instead of 1 cobblestone = 1 stone, and the pattern provider will insert 8 cobblestone into your smelting setup every operation instead of one at a time.