Cubic smoothing spline error measure weights

How exactly does the error measure weights work in csaps cubic smoothing spline function?

What does it mean by error measure weights? I have read the documentation through but it is unclear to me.

I would like to construct a smoothing spline based on weights of each spline, meaning that ones with greater weight value should be considered more for the spline. (i.e. something with a weight of 0.1 would be considered more of an outlier compared to something with a weight of 0.9) Is this how it works in csaps?

It would be great if there was some kind of mathematical explanation of how csaps works.