Stack Exchange network consists of 183 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.
$\begingroup$When you reach 1000 reputation, you may create tags yourself. We find it best that someone have more experience before making changes.$\endgroup$
$\begingroup$To add one more minor correction to what @GeraldEdgar wrote, MO currently has privilege to create tags at 300 reputation points. There are some sites where this privilege is set to 1000 reputation points, on such example is Mathematics.$\endgroup$