When it comes to working with SOLIDWORKS every single part has a coordinate system. This is important because you are working in 3D space in SOLIDWORKS. This sometimes presents inherent complexities with navigating around your parts, especially with assemblies. One trick to make this process a little more intuitive and easier to understand is to leverage the power of coordinate systems. Each part will always have at least one. This is the intersection of the front, top and right planes, or in x,y,z coordinate terms it’s the origin 0,0,0. Just think about it as the home for your part.
It’s good to know where this is because it’s useful to leverage this in mating parts together in assemblies, setting up a simulation and countless other applications. But sometimes this one coordinate system isn’t enough. It’s frequently necessary or useful to create your own custom coordinate. The biggest use case for this is when exporting your models for 3D printing or use by other engineers because you can control the orientation of the model with a custom coordinate system.