If I create a chart manually, and try to add a second or third series, the
SourceData dialog displays only "Name and "Values" and "Category X axis
labels".

Someone sent me a chart with multiple series, and when I look at the
SourceData dialog, I see: "Name", "XValues" and "YValues".

What are XValues and YValues? How do I create a chart with an Xvalue and a
YValue?

Thanks in advance.