If you wish to have cross-references in a document with numbered
sections, use \label{name} to label the point in your document
with some mnemonic, and Section \ref{name} to refer to that
point. \ref{name} will be replaced by the number of the
section containing the corresponding \label command. As with
your bibliography citations, you will need to run LaTeX twice
to generate these references.
Practice:
Create a fake document with many numbered sections and lots of cross references.