The Assembly Outline is used to create drawings for assembly. These drawings help people putting the components on the PCB to check they're in the right place. The Assembly Outline shows the smallest, average, and largest dimensions of the parts and often points out which way is "Pin 1." It also has a label showing which part it is.

The Component Outline, on the other hand, only shows the average size of the part and doesn't say which way is "Pin 1." It's linked to the Terminal Outlines and doesn't have a label. The Component Outline helps designers see how much space each part takes up on the PCB. This is useful for making sure parts don't overlap and there's enough space between them.

Both outlines are needed because they're used at different times when making a PCB. The Assembly Outline is essential for putting the parts together correctly, while the Component Outline helps in the design phase. It's important to have both to make sure the PCB is made and put together smoothly.

The Component Outline is only mapped to the Nominal package dimensions and does not indicate Pin 1 Polarity. The Component Outline is associated with the Terminal Outlines and does not have a reference designator. 

The Component and Assembly Outlines are placed on different layers and their outline widths can be independently assigned. 

In Tools > Options, the user can turn on/off any Drafting Outline. 

We add features based on customer requests. Someone asked for the Nominal Component Outline with Terminal Outlines. But if you don't see any value with this outline, turn it off. 

I just realized that I've been blindly including both of these in my footprints, both sized to the maximum material condition, but on their own layers (obviously), and I don't really understand why. Can someone please explain the purpose behind having both an Assembly Outline and Component Outline in a footprint? It seems like they are both communicating identical information.

Thank you,

Chris