We currently have

https://matplotlib.org/gallery/lines_bars_and_markers/line_styles_reference.html
https://matplotlib.org/gallery/lines_bars_and_markers/linestyles.html

which are partly redundant. Also one of them uses the (offset, on-off-dash-seq) but does not explain it.

This should be merged in to a single comprehensible file with a bit more explanation.

See also:
https://matplotlib.org/api/_as_gen/matplotlib.lines.Line2D.html#matplotlib.lines.Line2D.set_linestyle
(which itself is not in great shape)