The planner calculates production chains. Give it a target output to work out recipes, machine counts, clock speeds and power draw. Or connect the machines yourself and let it check the flows. It uses the same data as the wiki pages for Items, Recipes and Buildings.
How it fits together
A factory you plan doesn't live in isolation. On the map, resource nodes can be linked straight into a factory's inputs, and factories can be linked to each other so that one factory's output feeds another's input across the world. Inside a signed-in world, all of this (factories, their links, the map layout and the world's own resource-node seed) is saved and can be revisited or shared; without an account it stays in your browser for the current session.
This category
The full walkthrough is in Using SatisfactoryBase. It covers the solver results, manual connections, map links, node settings and saving your work. If you are just getting started, try Quick start with SatisfactoryBase first.