Modular Machines adds a Machine Frame that provides a 5x5 Module grid. You can socket Modules into these slots, specify the flow of execution (It always starts in the upper left slot). Each Module causes a specific event to happen, pulling items out of the input slot, placing blocks in the world, breaking them, smelting... etc.
Each modules tooltip tells you what inputs it requires to function, and what outputs it leaves in the machine frame, so you can easily tell which modules work together.
(This discription will improve after modoff is over, deadlines are wonderful things.)
The image shows a Quarry, that will also ore double and smelt any ores it mines for you.
