Hello Wei,

The "coded" units refer to orthogonalized (independent) factors--said to be on a common scale, whereas the "uncoded" units are not. Like standardized regression coefficients, coded units allow you to make relative comparisons of emphasis on specific IVs/factors in your design, whereas uncoded (more akin to traditional, unstandardized regression coefficients) do not.

Here's a brief explanation: https://support.minitab.com/en-us/minitab/18/help-and-how-to/modeling-statistics/doe/supporting-topics/basics/coded-units-and-uncoded-units/

Good luck with your work.

Good point David

Note that after running the data, you obtain an orthogonalized components (PCA). Then you verimax rotate the PCA, you obtain the FA provided your eigen value `> or = 1. So use the verimax rotated data for your FA.