See what path aliases are set up with Drush? Ive installed Drush and my local system is a Mac. It seems to have worked as when I type drush into the terminal a long list of commands comes up.

When I type drush cc all I get the message 'drush' cache was cleared . Does that mean my path aliases are set up? Or could I be getting a false success message? I have a number of Drupal sites locally and I dont know which (if any) is having its cache cleared.
You have to either be within a drupal doc_root (aka apache verbiage) or have properly configured drush site aliases for commands to work:

Eg, if your site lives at /var/www/

cd /var/www/
drush cc all


Or if you have setup a drush site alias of @local, then from anywhere on your system:

drush @local cc all