With a few exceptions, sphinx markup is a superset of docutils restructured text.
In your sphinx installation, the doc directory contains sphinx-generated html as well as the source rst files. You can regenerate html or pdf with the sphinx-build command.
This documentation contains an introduction to restructured text markup, but you will probably need to consult some more detailed docutils ReSt documentation (e.g. docutils ReSt quickref)
Some initial pointers:
Note