Here
https://www.w3schools.com/xml/schema_complex_empty.asp
I found this
but here
https://www.xml.com/pub/a/2001/08/22/easyschema.html
i found this
https://www.xml.com/pub/a/2001/08/22/examples/schematree.pdf
this schema
why w3schools use ComplexContent instead of SimpleContent?